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GIFT   OF 

MICHAEL  REESE 


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MANUAL 


OF 


IRRIGATION  ENGINEERING 


BY 


HERBERT   M,   WILSON,   C.E. 


FIRST  EDITION, 

FIRST   THOUSAND. 


NEW  YORK: 
JOHN    WILEY    &    SONS, 

53  EAST  TENTH  STREET. 
1893. 


,5-0  67$ 


COPYRIGHT,  1893, 

BV 
HERBERT  M.  WILSON. 


ROBERT  DKUMMOND, 

Electrotyper. 

444  &  446  Pearl  Street, 

New  York. 


PREFACE. 


THE  need  of  a  comprehensive  treatise  on  irrigation  has 
been  so  frequently  brought  to  my  attention  during  the  last 
few  years,  that  I  have  undertaken  to  write  this  book  with  the 
hope  that  it  may  help  those  who  are  engaged  in  the  study 
or  practice  of  irrigation  engineering.  It  is  chiefly  the  result  of 
original  investigation,  the  descriptions  of  works  being  made 
from  personal  observation  in  America,  Europe,  and  India. 

Some  of  the  matter  contained  in  Part  I  is  compiled,  and  in 
its  preparation  I  am  especially  indebted  for  information  and 
suggestions  to  the  valuable  work  on  "  Water  Supply  Engineer- 
ing," by  Mr.  J.  T.  Fanning.  There  is  added,  however,  much 
that  is  new,  a  portion  of  which  was  obtained  from,  the  reports 
of  Mr.  F.  H.  Newell,  Chief  Hydrographer  of  the  U.  S.  Geo- 
logical Survey.  The  purpose  has  been  to  include  in  Part  I 
only  so  much  of  hydraulics  as  is  an  indispensable  preliminary 
to  the  remainder  of  the  book,  or  is  original  matter.  Wherever 
the  subject  has  been  treated  by  others  the  reader  is  referred 
to  their  works. 

The  entire  book  relates  directly  to  the  conditions  surround- 
ing Western  irrigation  practice.  The  examples  given  and  the 
suggestions  made  apply  immediately  to  Western  methods, 
though  many  useful  hints  a**e  borrowed  from  foreign  experi- 
ence. The  classification  adopted  is  original,  I  believe,  and 
follows  closely  that  employed  in  reports  made  by  me  to  the 
Government,  which  seem  to  have  met  with  general  approval. 
In  this  classification  the  terms  "diversion  weirs  "  and  "dams*1 

iii 


*V  PREFACE. 

have  been  used  with  special  signification.  Under  the  term 
"diversion  weirs"  are  included  all  obstructions  built  across 
running  streams  and  designed  to  act  as  overflow  weirs,  though 
their  functions  may  be  those  either  of  storage  dams  or 
diversion  weirs  or  both.  Under  the  term  "dams"  are  in- 
cluded all  retaining  walls,  of  whatsoever  material,  which  are 
intended  only  to  impound  water  and  are  not  so  constructed  as 
to  withstand  the  shock  of  falling  water.  These  classes  neces- 
sarily overlap  to  some  extent. 

The  subject  of  the  application  of  water  to  crops  is  but 
briefly  touched  upon.  It  would  in  itself  require  a  volume, 
and  is  one  of  more  interest  to  the  farmer  than  to  the  engineer. 
Part  III,  which  treats  of  storage  works,  contains  much  new  ma- 
terial never  before  brought  together,  and  this  is  especially  true 
of  the  chapters  on  Earth  Dams  and  Pumping.  The  theory 
of  high  masonry  dams  is  but  briefly  considered,  as  this  subject 
has  already  been  exhaustively  treated  by  previous  writers,  to 
whose  works  reference  is  made.  What  little  has  been  said 
concerning  it  is  partly  compiled,  the  chief  source  being  Weg- 
mann's  admirable  treatise  on  masonry  dams.  Great  care  has 
been  taken  throughout  the  volume  to  avoid  the  use  of  mathe- 
matics, since  many  of  the  formulas  given  on  the  flow  of  water 
in  open  or  closed  channels,  on  the  discharge  from  catchment 
basins,  and  on  strains  in  masonry  dams  are  exceedingly  faulty 
and  misleading.  We  have  much  to  learn  before  we  can  apply 
mathematics  to  these  subjects  with  accuracy.  I  consider  it 
better  to  follow  practical  usage  and  experience  than  theory 
where  the  latter  is  founded  on  doubtful  premises  and  is  liable 
to  produce  inaccurate  results  if  adhered  to  closely. 

The  endeavor  has  been  to  prepare  a  work  which  will  be  of 
value  to  the  practical  engineer  as  well  as  to  the  student.  It 
was  found  impossible  to  include  within  the  covers  of  one 
volume  the  necessary  tables  on  hydraulics  and  flow  of  water. 
It  is  believed,  however,  that  this  book  contains  much  that  will 
be  useful  to  the  practical  engineer,  and  that  the  teacher  of 
irrigation  engineering  will  find  the  facts  assembled  in  such 
manner  as  to  be  materially  helpful. 


rREFA  CE.  v 

The  effort  has  been  to  illustrate  all  the  important  works 
described,  as  well  as  types  of  works,  in  order  that  practising 
engineers  may  obtain  suggestions  from  the  experience  of 
others. 

I  am  indebted  to  the  courtesy  of  the  Director  of  the  U.  S. 
Geological  Survey  for  numerous  electrotypes  of  illustrations, 
which  had  been  previously  published  in  reports  made  by  me. 
Several  illustrations  were  also  obtained  through  the  courtesy 
of  the  Secretary  of  the  American  Society  of  Civil  Engineers, 
being  electrotypes  of  those  used  in  papers  read  by  me  before 
that  society. 

WASHINGTON,  D.  C.,  January,  1893. 


CONTENTS. 


CHAPTER  I. 

INTRODUCTION. 
ART.  PAGE 

1.  Extent  of  Irrigation i 

2.  Control  of  Irrigation  Works i 

3.  Value  as  an  Investment 2 

4.  Incidental  Values 2 

5.  Cost  and  Returns  of  Irrigation 3 


PART   I. 

HYDROGRAPHY. 
CHAPTER   II. 

PRECIPITATION. 

6.  Relation  of  Rainfall  to  Irrigation 5 

7.  General  Rainfall  Statistics 6 

8.  Rainfall  Distribution  in  Detail   6 

9.  Great  Rainfalls 7 

10.  Suddenness  of  Great  Storms 8 

1 1 .  Precipitation  on  River  Basins 9 

12.  Rainfall  Statistics  by  States 9 

13.  Gauging  Rainfall " 

14.  Works  of  Reference:  Rainfall 12 

vii 


Vlll  CONTENTS. 

CHAPTER  III. 

EVAPORATION   AND    ABSORPTION. 
ART.  PAGE 

15.  Evaporation  Phenomena 13 

16.  Measurement  of  Evaporation 13 

17.  Amount  of  Evaporation 15 

18.  Evaporation  from  Snow  and  Ice  17 

19.  Evaporation  from  Earth 18 

20.  Effect  of  Evaporation  on  Water  Storage 18 

21.  Percolation  and  its  Amount 18 

22.  Absorption 19 

23.  Amount  of  Absorption  in  Reservoirs  and  Canals. ... 20 

24.  Prevention  of  Percolation 20 

25.  Seepage  Water 21 

CHAPTER  IV. 

RUNOFF   AND   FLOW   OF    STREAMS. 

26.  Runoff 22 

27.  Variability  of  Runoff 22 

28.  Formulas  for  Runoff 23 

29.  Examples  of  Runoff s 24 

30.  Flood  Discharges  of  Streams 25 

31.  Discharge  in  Seasons  of  Minimum  Rainfall 25 

32.  Regimen  of  Western  Rivers 25 

33.  Mean  Discharge  of  Streams 27 

34.  Available  Annual  Flow  of  Streams 27 

35.  Works  of  Reference:  Evaporation,  Percolation,  and  Runoff 27 

CHAPTER  V. 

SUBSURFACE  WATER   SOURCES. 

36.  Sources  of  Earth  Waters 28 

37.  Sources  of  Springs  and  Artesian  Wells 28 

38.  Artesian  Wells 29 

39.  Examples  of  Artesian  Wells 29 

40.  Supplying  Capacity  of  Wells 30 

41.  Tunneling  for  Water , 30 

42.  Other  Subsurface  Water  Sources 30 

43.  Works  of  Reference :  Artesian  Wells 31 

CHAPTER  VI. 

ALKALI,  DRAINAGE,    AND   SEDIMENTATION. 

44.  Harmful  Effects  of  Irrigation 32 

45.  Alkali 32 


CONTENTS.  ix 

ART-  PACK 

46.  Causes  of  Alkali 32 

47.  Waterlogging 33 

48.  Prevention  of  Alkali  and  Waterlogging , 33 

49.  Chemical  Treatment  and  Leaching 34 

50.  Drainage 34 

51.  Excessive  Use  of  Water 34 

52.  Silt  35 

53.  Amount  of  Sediment v 35 

54.  Prevention  of  Sedimentation  in  Reservoirs  and  Canals 35 

55.  Fertilizing  Effects  of  Sediment 36 

56.  Weeds  37 

CHAPTER  VII. 

QUANTITY  OF  WATER  REQUIRED. 

57.  Duty  of  Water 38 

58.  Units  of  Measure  for  Water  Duty  and  Flow 38 

59.  Measurement  of  Water  Duty 40 

60.  Duty  per  Second-foot 40 

61.  Depth  of  Water  required  to  Soak  Soil 41 

62.  Duty  per  Acre-foot 42 

63.  Linear  and  Areal  Duty 42 

64.  Percentage  of  Waste  Land 42 

65.  Works  of  Reference:  Alkali,  Sedimentation  and  Duty  of  Water 43 

CHAPTER  VIII. 

PRESSURE   AND   MOTION   OF  WATER. 

66.  Physical  and  Chemical  Properties  of  Water 44 

67.  Weight  of  Water 44 

68.  Pressure  of  Water 45 

69.  Amount  of  Pressure  of  Water 45 

70.  Center  of  Pressure 46 

71.  Atmospheric  Pressure 46 

72.  Motion  of  Water 46 

CHAPTER   IX. 

FLOW    AND    MEASUREMENT    OF    WATER    IN    OPEN   CHANNELS. 

73.  Factors  affecting  Flow 48 

74.  Formulas  of  Flow  in  Open  Channels 49 

75.  Kutter's  Formula 49 

76.  Discharge  of  Streams  and  Velocities  of  Flow 5* 

77.  Surface  and  Mean  Velocities  52 


CONTENTS. 


78.  Measuring  or  Gauging  Stream  Velocities 52 

79.  Current  Meters 53 

80.  Gauging  Stations 54 

81.  Use  of  the  Current  Meter 55 

82.  Rating  the  Meter 55 

83.  Rating  the  Station 56 

84.  Measuring  Weirs 57 

85.  Rectangular  Measuring  Weir 57 

86.  Francis'  Formulas 58 

87.  Conditions  of  using  Rectangular  Weir 58 

88.  Trapezoidal  Weirs 59 

89.  Weir  Gauge  Heights 61 

90.  Measurement  of  Canal  Water 61 

91.  Methods  of  Measurement 62 

92.  The  Statute  Inch  or  Module ....«-. 62 

93.  Foote's  Water  Meter 63 

94.  Rating  Flumes 64. 

95.  Divisors 65 

96.  Works  of  Reference:  Hydraulics 65 


PART  II. 

CANALS  AND  CANAL   WORKS. 
CHAPTER  X. 

CLASSES   OF  IRRIGATION  WORKS. 

97.  Gravity  and  Lift  Irrigation 66 

98.  Navigation  and  Irrigation  Canals 67 

99.  Sources  of  Supply 67 

100.  Perennial  Canals 68 

101.  Dimensions  and  Cost  of  some  Perennial  Canals 69 

102.  Parts  of  a  Canal  System 69 

CHAPTER  XI. 

ALIGNMENT,    SLOPE,    AND  CROSS-SECTION. 

103.  Location  of  Headworks 72 

104.  Diversion  Line 72 

105.  Relation  between  Lands  and  Water  Supply 72 

106.  Survey  and  Alignment 73 

107.  Obstacles  to  Alignment 74 


CONTENTS.  xi 

ART.  PAGE 

108.  Sidehill  Canal  Work 74 

IOQ.  Curvature 75 

1 10.  Borings,  Trial  Pits,  and  Permanent  Marks 76 

in.  Example  of  Canal  Alignment — Ganges  Canal 76 

112.  Example  of  Canal  Alignment — Turlock  Canal  79 

113.  Slope  and  Cross-section 85 

114.  Limiting  Velocity 86 

115.  Grade  for  Given  Velocities 87 

116.  Examples  of  Canal  Grades 87 

117.  Cross-sections 88 

118.  Form  of  Cross-section 89 

119.  Side  Slopes  and  Top  Width  of  Banks 91 

120.  Cross-section  with  Subgrade 92 

121.  Shrinkage  of  Earthwork 93 

122.  Cross-section  in  Rock 93 

CHAPTER  XII. 

HEADWORKS  AND   DIVERSION  WEIRS. 

123.  Location  of  Headworks 95 

124.  Character  of  Headworks 96 

125.  Diversion  Weirs 97 

126.  Classes  of  Weirs 98 

127.  Brush  and  Bowlder  Weirs. 98 

128.  Rectangular  Pile  Weirs 99 

129.  Open  and  Closed  Weirs 99 

130.  Open  Frame  or  Flashboard  Weirs 101 

131.  Open  Masonry  Weirs,  Indian  Type ,  104 

132.  Wooden  Crib  and  Rock  Weirs in 

133.  Construction  of  Crib  Weirs 115 

134.  Composite  Gravel  and   Rock  Weir 115 

135.  Scouring  Effect  of  Falling  Water 1 16 

136.  Weir  Aprons 117 

137.  Rollerway  and  Ogee-shaped  Weirs 118 

138.  Water-cushions 119 

139.  Masonry  Weirs ...  121 

140.  Masonry  Weirs  founded  on  Piles 122 

141.  Masonry  Weir  founded  on  Piles  and  Cribs 122 

142.  Masonry  Weir  founded  on  Cribs 123 

143.  Masonry  Weirs  founded  on  Wells 126 

144.  Weirs  founded  on  Rock. — San  Diego  Weir 126 

145.  Henares  Weir 127 

146.  Appleton  Weir 128 

147.  Vir  Weir 129 

148.  Other  Masonry  Weirs 129 

149.  Diversion  Dams I3l 


XI 1  CONTENTS. 

CHAPTER  XIII. 

SCOURING  SLUICES,  REGULATORS,  AND   ESCAPES. 

ART.  PAGE 

150.  Scouring  Sluices 133 

151.  Examples  of  Scouring  Sluices 135 

152.  Automatic  Sluice  Gates 136 

153.  Mahanuddy  Sluice  Shutters. ...    137 

1 54.  Soane  Automatic  Sluice  Gates 138 

155.  Relation  of  Weirs  to  Regulators 139 

156.  Classification  of  Regulators 143 

157.  General  Form  of  Regulator, 144 

158.  Arrangement  of  Canal  Head 144 

159.  Wooden  Flashboard  Regulators 146 

160.  Wooden  Regulator  Gate  lifted  by  Lever 146 

161.  Wooden  Gate  lifted  by  Windlass , 147 

162.  Gate  lifted  by  Travelling  Winch 148 

163.  Gate  raised  by  Gearing  or  Screw 148 

164.  Rolling  Regulator  Gate 151 

165.  Hydraulic  Lifting  Gate 153 

166.  Escapes . 154 

167.  Location  and  Characteristics  of  Escapes 155 

168.  Design  of  Escape  Heads 156 

169.  Sand  Gates 157 


CHAPTER  XIV. 

FALLS  AND    DRAINAGE  WORKS. 

170.  Excessive  Slope 159 

171.  Falls  and  Rapids 160 

172.  Retarding  Velocity  by  Flashboards  on  Fall  Crest 160 

1 73.  Retarding  Velocity  by  contracting  Channel 161 

174.  Gratings  to  retard  Velocity  of  Approach 161 

175.  Simple  Vertical  Fall  of  Wood 162 

176.  Wooden  Fall  with  Water-cushion 165 

177.  Masonry  Falls 167 

178.  Wooden  Rapids  or  Chutes  167 

179.  Masonry  Rapids 169 

180.  Drainage  Works 169 

181.  Drainage  Cuts 169 

182.  Inlet  Dams 170 

183.  Level  Crossings , 170 

184.  Flumes  and  Aqueducts 172 

185.  Sidehill  Flumes 173 

186.  Construction  of  Flumes 175 

187.  Flume  Trestles 177 


CONTENTS.  xiii 

AKT-  PAGE 

188.  Iron  Aqueducts I77 

189.  Masonry  Aqueducts 181 

190.  Superpassages 181 

191.  Inverted  Siphons 183 

192.  Inverted  Siphon  of  Wood 185 

193.  Inverted  Siphons  of  Masonry 187 


CHAPTER  XV. 

DISTRIBUTARIES. 

194.  Object  and  Types 191 

195.  Location  of  Distributaries jgi 

196.  Design  of  Distributaries 193 

197.  Efficiency  of  a  Canal 194 

198.  Private  Watercourses 196 

199.  Dimensions  of  Distributaries 197 

200.  Distributary  Channels  in  Earth 198 

201.  Wooden  Distributary  Heads 198 

202.  Masonry  Distributary  Heads 201 

203.  Iron  and  Steel  Distributary  Pipes 201 

204.  Wooden  Distributary  Pipes  201 

205.  Rotation  in  Water  Distribution 202 


CHAPTER  XVI. 

APPLICATION   OF    WATER,    AND   PIPE  IRRIGATION. 

206.  Methods  of  Applying  Water .  204 

207.  Sidehill  Flooding  of  Meadows 205 

208.  Flooding  by  Checks 206 

209.  Flooding  by  Checkerboard  System  of  Squares 207 

210.  Flooding  by  Terraces 208 

211.  Furrow  Irrigation  of  Vegetables  and  Grain 209 

212.  Combined  Flooding  and  Furrow  Irrigation  of  Orchards 210 

213.  Irrigating  Orchards  by  Small  Furrows 211 

214.  Subsurface  Irrigation 212 

215.  Sub-irrigation  Pipes 212 

216.  Method  of  Laying  Pipes 213 

217.  Measuring  Sub-irrigation  Waters 214 

218.  Works  of  Reference:  Canals  and  Canal  Works 214 


XIV  CONTENTS. 

PART   III. 

STORAGE  RESERVOIRS. 
CHAPTER  XVII. 

LOCATION  AND    CAPACITY   OF   RESERVOIRS. 
ART.  PAGE 

219.  Classes  of  Storage  Works 216 

220.  Relation  of  Reservoir  Site  to  Land  and  Water  Supply 216 

221.  Character  of  Reservoir  Site 218 

222.  Topography  and  Survey  of  Reservoir  Sites 218 

223.  Geology  of  Reservoir  Sites 219 

224.  Cost  and  Dimensions  of  some  Great  Storage  Reservoirs 222 

CHAPTER  XVIII. 

EARTH   AND   LOOSE-ROCK   DAMS. 

225.  Earth  Dams  or  Embankments 223 

226.  Dimensions  of  Earth  Dams 224 

227.  Foundations. . . '. 225 

228.  Foundations  of  Masonry  Core  and  Puddle  Wall 226 

229.  Springs  in  Foundations 227 

230.  Masonry  Cores,  Puddle  Walls,  and  Homogeneous  Embankments....  227 

231.  Masonry  Cores 229 

232.  Puddle  Walls  and  Faces 230 

233.  Puddle  Trench 231 

234.  Construction  of  Embankment 231 

235.  Homogeneous  Earth  Embankment 233 

236.  Embankment  Material 234 

237.  Interior  Slope  and  Paving 235 

238.  Earth  Embankment  with  Masonry  Retaining  Wall 237 

239.  Earth  and  Loose-rock  Dams. — Pecos  Dam 239 

240.  Loose  Rock  and  Earth  Dam. — Idaho  Dam 240 

241.  Loose-rock  Dams 242 

242.  Walnut  Grove  Dam 243 

243.  Crib  Dams 244 

244.  Loose-rock  Dam  with  Masonry  Retaining  Walls 246 

CHAPTER  XIX. 

MASONRY   DAMS. 

245.  Theory  of  Masonry  Dams 248 

246.  Stability  of  Gravity  Dams 249 

247.  Stability  against  Sliding 251 

248.  Coefficient  of  Friction  in  Masonry 252 


CONTENTS.  XV 

ART.  PACK 

249.  Stability  against  Crushing 254 

250.  Limiting  Pressures 255 

251.  Stability  against  Overturning 256 

252.  Molesworth's  Formula  and  Profile  Type 259 

253.  Height  and  Top  Width  of  Dam 260 

254.  Profile  of  Dam 260 

255.  Curved  Masonry  Dams 261 

256.  Design  of  Curved  Dam 265 

257.  Foundations 267 

258.  Material  of  which  Constructed. — Ashlar  Masonry 267 

259.  Concrete 268 

260.  Rubble  Masonry 270 

261.  Cement 271 

262.  Details  of  Construction 271 

263.  Submerged  Dams 273 

264.  Construction  in  Flowing  Streams 274 

265.  Specifications  and  Contracts 275 

266.  Examples  of  Masonry  Dams 276 

267.  Furens  Dam,  France 276 

268.  Gran  Cheurfas  Dam,  Algiers 278 

269.  Tansa  Dam,  India 279 

270.  Bhatgur  Dam,  India 281 

271.  New  Croton  Dam,  New  York 282 

272.  Periar  Dam,  India 285 

273.  Beetaloo  Dam,  South  Australia 287 

274.  San  Mateo  Dam,  California ...   287 

275.  Sweetwater  Dam,  California 289 

276.  Vyrnwy  Dam,  Wales 289 

277.  Betwa  Dam,  India 291 

278.  Turlock  Dam ,  California 295 

279.  Folsom  Dam,  California 295 

280.  Colorado  River  Dam,  Texas 297 

281.  Bear  Valley  and  Zola  Dams 298 

282.  Works  of  Reference  :  Storage  Works 300 


CHAPTER  XX. 

WASTEWAYS   AND   OUTLET   SLUICES. 

283.  Wasteways 301 

284.  Character  and  Design  of  Wasteways 302 

285.  Discharge  of  Waste  Weirs 3<>2 

286.  Classes  of  Wasteways 3°4 

287.  Shapes  of  Waste  Weirs 305 

288.  Examples  of  Wasteways 3°5 


XVI  CONTENTS. 

ART.  PAGE 

289.  Automatic  Shutters  and  Gates 306 

290.  Undersluices 309 

291.  Examples  of  Undersluices 309 

292.  Outlet  Sluices 310 

293.  Gate  Towers  and  Valve  Chambers 312 

294.  Examples  of  Gate  Towers  and  Outlet  Sluices 314 

CHAPTER  XXI. 

PUMPING,  TOOLS,  AND   MAINTENANCE. 

295.  Underground  Cribwork  or  Tunnels 316 

296.  Tunnelling  Underground ....  317 

297.  Pumping  or  Lift  Irrigation .  317 

298.  Windmills  and  Elevators   319 

299.  Water-wheels 319 

300.  Steam  Pumps 321 

301.  Centrifugal  Pumps 322 

302.  Huffer  and  Nye  Pumps 323 

303.  Pumping  Engines 323 

304.  Irrigation  Tools 324 

305.  Scrapers 325 

306.  Excavating  Machines 326 

307.  Maintenance  and  Supervision  of  Canal  Works 328 

308.  Sources  of  Impairment  of  Irrigation  Works ...    328 

309.  Inspection 329 

310.  Works  of  reference  :  Pumping  Machinery  and  Water 320 

TABLES. 

I.  Extent  and  Cost  of  Irrigation 3 

II.   Precipitation  by  River  Basins 9 

III.  Precipitation  by  States 10 

IV.  Depth  of  Evaporation  per  Month  in  1887-88 16 

V.  Depth  of  Evaporation  per  Month  in  Inches 17 

VI.  Units  of  Measure 39 

VII.  Duty  of  Water 41 

VIII.  Value  of  C  for  Earthen  Channels  by  Kutter's  Formula  : 50 

IX.  Discharge  over  Rectangular  Weirs 60 

X.  Some  great  Perennial  Canals 70 

XI.  Cost  and  Dimensions  of  some  Storage  Reservoirs 221 

XII.  Coefficients  of  Friction  in  Masonry 252 

XIII.  Wegmann's  Practical  Profile  No.  3 262 


LIST   OF   ILLUSTRATIONS. 


PAGB 

I.   Plan  and  Cross-section  of  Ganges  Canal,  Hurdwar  to  Roorkee, 

India , 75 

II.   Kern  River  Diversion  Weir.     Head  of  Galloway  Canal 102 

III.  Cross-sections  of  Indian  Weirs 104 

IV.  View  of  Weir  and  Scouring  Sluices,  Head  of  Arizona  Canal no 

V.  Cross-section  of  Croton  Dam   124 

VI.  Automatic  Sluice  Gate.     Soane  Canal,  India 140 

VII.  Bear   River    Canal.     Elevation   and  Cross-section  of  Weir  and 

Regulator 150 

VIII.  Cross-section  and  Elevation  of  Regulator  Gates,  Folsom  Canal..  152 

IX.  View  of  Fall  on  Arizona  Canal 164 

X.  Cross-section  of  Kushuk  Fall,  Agra  Canal,  India 166 

XI.  Plan  of  Rapids,  Bari  Doab  Canal,  India 168 

XII.   Highline  Canal,  Colorado.     View  of  Bench  Flume. 174 

XIII.  View  of  Pecos  Flume 176 

XIV.  View  of  Solani  Aqueduct,  Ganges  Canal,  India 180 

XV.   Elevation  and  Cross-section  of  Nadrai  Aqueduct,  Lower  Ganges 

Canal,  India 182 

XVI.  View  of  Ranipur  Superpassage,  Ganges  Canal,  India    184 

XVII.  Central    Irrigation  District  Canal.     Elevation  and  Cross-section 

of  Stony  Creek  Culvert 186 

XVIII.   Idaho  Irrigation  Company's  Canal.     View  of  Wooden  Siphon  on 

Phyllis  Branch 188 

XIX.  Standard  Masonry  Outlet  for  Distributaries,  Punjab,  India 200 

XX.  Cross-section  of  Ashti  Dam,  India 232 

XXI.  View  of  Pecos  Dam 23$ 

XXII.  View  of  Bhatgur  Dam,  India 280 

XXIII.  San  Mateo  Dam.     Plan,  Cross-section,  and  Outlet  Sluices 286 

XXIV.  Plan  of  Sweetwater  Dam 288 

xvii 


XV111  LIST  OF  ILLUSTRATIONS. 

PLATE  PAGK 

XXV.   Cross-section  of  Svveetvvater  Dam 290 

XXVI.  View  of  Svveetwater  Dam 292 

XXVII.   Folsom  Canal,  View  of  Weir  and  Regulator 294 

XXVI II.  Folsom  Canal,  Plan  and  Cross-section  of  Weir 296 

XXIX. .Plan,  Elevation,  and  Cross-section  of  Reinold's  Automatic  Waste 

Gate,  India 308 

FIGURE 

1.  Rain  Gauge n 

2.  Evaporating  pan 14 

3.  Maximum,  Minimum,  and  Mean  Discharge  of  some  Western  Rivers..  26 

4.  Colorado  Current  Meter 53 

5.  Haskel!  Current  Meter 54 

6.  Rectangular  Measuring  Weir 57 

7.  Foote's  Measuring  Weir,  A.       Water  Divisor,  B 63 

8.  Canal  Cross-sections  for  Varying  Bed-widths 75 

9.  Turlock  Canal.     Plan  of  Diversion  Line So 

10.  Turlock  Canal.     View  of  Sidehill  Work Si 

11.  Turlock  Canal.     View  in  Tunnel 82 

12.  Various  Canal  Cross-sections 90 

13.  Cross-section  of  Calloway  Canal  showing  Subgrade. .  .   92 

14.  Rock  Cross-section.    Tnrlock  Canal 93 

15.  Rock  Cross-section.     Bear  River 94 

16.  Open  Weir,  Monte  Vista  Canal 101 

17.  Cross-section  of  Open  Weir,  Calloway  Canal 103 

18.  Half-elevation  and  Plan,  and  Section  of  Soane  Weir,  India 106 

19.  Elevation  and  Cross-section  of  Sidhnai  Weir,  India 108 

20.  View  of  Open  Weir  on  River  Seine,  France 109 

21.  Cross-section  of  Arizona  Weir 112 

22.  Cross-section  of  Bear  River  Weir 112 

23.  Cross-section  of  Hoi  yoke  Weir .- .  114 

24.  Cross-section  of  Little  Kukuna  Weir 116 

25.  Diagram  of  Ogee  Curve , 118 

26.  Cross-section  of  Norwich  Water  Power  Company's  Weir 123 

27.  Plan,  Elevation,  and  Cross-section  of  San  Diego  Weir 127 

28.  Cross-section  of  Henares  Weir,  Spain 128 

29.  Cross-section  of  Appleton  Weir 128 

30.  Cross-sections  of  Newark  Dam  and  Weir 13° 

31.  Cross-section  of  Lawrence  Weir 131 

32.  View  of  Highline  Canal  Weir 134 

33.  Cross-section  of  Mahanuddy  Automatic  Shutters,  India 137 

34.  Plan  of  Headworks,  Ganges  Canal,  India 142 

35.  Arizona  Canal.     Plan  of  Headworks 143 

36.  Regulator  Gates,  Ganges  Canal 147 

37.  Regulator  Gates,  Soane  Canal 148 

38.  Regulator  Gates,  Arizona  Canal 149 


LIST   OF  ILLUSTRATIONS.     .  XIX 

FIGUKB  PACK 

39.  Regulator  Gates,  Del  Norte  Canal 149 

40.  Sliding  Regulator  Gate,  Idaho  Canal 151 

41.  Rolling  Regulator  Gate,  Idaho  Canal 153 

42.  Longitudinal  Section  of  Fall,  Arizona  Canal 162 

43.  Plan  and  Cross-section  of  Fall,  Bear  River  Canal 163 

44.  Cross-section  of  Fall,  Turlock  Canal 165 

45.  Plan  and  Elevation  of  Big  Drop,  Grand  River  Canal 167 

46.  Plan  of  Rutmoo  Crossing,  Ganges  Canal,  India 171 

47.  Cross-section  of  San  Diego  Flume 175 

48.  Bear    River   Canal.     Elevation  and  Cross-section   of  Iron  Flume  on 

Corinne  Branch 178 

49.  Aqueduct,  Henares  Canal,  Spain 179 

50.  Section  of  Wooden  Siphon,  Del  Norte  Canal 185 

51.  Soane  Canal.     Cross-section  of  Kao  Nulla  Siphon-aqueduct 187 

52.  Sections  of  Sesia  Siphon,  Cavour  Canal,  Italy 189 

53.  Diagram  illustrating  Distributary  System 192 

54.  View  of  Distributary  Head,  Calloway  Canal 199 

55.  Plan  of  Bifurcation,  Del  Norte  Canal 199 

56.  Colorado  Wooden  Pipe 202 

57.  Diagram  illustrating  Flooding  of  Meadows 205 

58.  Irrigation  by  System  of  Check-levees 206 

59.  Flooding  by  System  of  Squares  208 

60.  Furrow  Irrigation  of  Grain 209 

61.  Furrow  Irrigation  of  Orchards. . .    210 

62.  Alessandro  Hydrant « 214 

63.  Diagrams  illustrating  Geology  of  Reservoir  Site 220 

64.  Cross-sections  of  Kabra  Dam  (A)  and  Ekruk  Dam  (B),  India 237 

65.  Cross-section  of  Pecos  Dam 239 

66.  Plan  of  Idaho  Dam 241 

67.  Cross-section  of  Idaho  Dam 241 

68.  Elevation  and  Cross-section  of  Walnut  Grove  Dam 244 

69.  Plan  and  Cross-section  of  Bowman  Dam 245 

70.  Elevation,  Plan,  and  Cross-section  of  Castlewood  Dam 247 

71.  Theoretical  Triangular  Cross-section  of  Dam 251 

72.  Diagram  illustrating  Wegmann's  Formula 256 

73.  Molesvvorth's  Profile  Type 259 

74.  Comparison  of  Profile  Types 261 

75.  Practical  Profile  from  Wegmann 263 

76.  View  of  San  Fernando  Submerged  Dam. 273 

77.  Cross-section  of  Furens  Dam,  France 277 

78.  Cross-section  of  Gran  Cheurfas  Dam,  Algiers 278 

79.  Cross-section  of  Tansa  Dam,  India 279 

So.  Cross-section  of  Bhatgur  Dam,  India 281 

81.  Cross-section  of  Earth  Embankment,  New  Croton  Dam,  Cornell's 283 

82.  Cross-section  of  Masonry  Dam,  New  Croton  Dam,  Cornell's 284 


XX  LIST  OF  ILLUSTRATIONS. 

FIGURE  PACK 

83.  Cross-section  of  Overfall  Weir,  New  Croton  Dam,  Cornell's 284 

84.  Cross-^sections  of  Periar  Dam  and  Waste  Weir,  India 285 

85.  Cross-section  of  Beetaloo  Dam,  Australia 287 

86.  Cross-section  of  Vyrnwy  Dam,  Wales 291 

87.  Cross-section  of  Betvva  Dam,  India 293 

88.  Cross-section  of  Turlock  Dam 295 

89.  Cross-section  of  Colorado  River  Dam 297 

90.  Cross^section  of  Bear  Valley  Dam 2gd 

91.  Plan  and  Elevation  of  Bear  Valley  Dam   298 

92.  Cross-section  of  Zola  Dam,  France 29 ) 

93.  Cross-section  of  Shutter  on  Soane  Weir,  India 307 

94.  Cross-section  of  Earth  Dam 312 

95.  Valve-plug,  Sweetwater  Dam 313 

96.  Valve  Chamber  and  Valves 315 

97.  Gathering-cribs,  Citizens'  Water  Co.,  Denver. 316 

98.  View  of  Water-wheel ....  320 

99.  Buck  Scraper 325 

100.  New  Era  Excavator 327 


IRRIGATION    ENGINEERING. 


CHAPTER  I. 
INTRODUCTION. 

1.  Extent  of  Irrigation. — The  extent  to  which  irrigation 
can  be  practised  is  enormous.     The  total  area  irrigated  in  India 
is  about  25,000,000  acres,  in  Egypt  about  6,000,000  acres,  and 
in  Italy  about  3,700,000  acres.    In  Spain  there  are  500,000 acres, 
in  France  400,000  acres,  and  in  the  United  States  4,000,000 
acres  of  irrigated  land.     This  means  that  crops  are  grown  on 
39,000,000  acres  of  land  which  but  for  irrigation  would  be  barren 
and  unproductive.     In  addition  to  this  there  are  some  millions 
more  of  acres   cultivated  by  the  aid  of  irrigation   in  China, 
Japan,  Australia,  Algeria,  South  America,  ,and  elsewhere. 

2.  Control  of  Irrigation  Works.— The   development   of 
irrigation    has  resulted  in  many  legal   complications,  while  a 
diversity  of  social  and   physical  conditions  has  given  rise  to  a 
variety  of  methods  for  its  control.     Practically  all  the  works 
in  India  are  now  under  the  direct  control  of  the  government, 
which  employs  its  engineers  and  legal  staff,  owns  the  land  and 
the  water,  constructs  the  works,  and  collects  the  rentals  for 
the  use  of  water  and  land.     In  the  Piedmont  valley  of  Italy 
the  land  is  the  property  of  individuals,  and  in  some  cases  indi- 
viduals are  owners  of  the  irrigation  works.     In  the  case  of  the 
Cavour  canal,  however,  the  government  owns  and  operates  the 
works,  and  the  water  is  sold  to  the  cultivators.     In  the  United 
States  all  irrigation  works  are  the  property  of  individuals  who 
construct  and  maintain  them  and  collect  the  rentals  for  the 
use  of  water.     In  some  cases  the  same  individual  owns   both 


2  INTRODUCTION. 

land  and  water;  but  usually  farmers  and  irrigators  have  no 
property  interest  in  the  irrigation  works.  These  are  owned 
and  operated  by  independent  organizations  who  collect  a  reve- 
nue from  the  sale  or  rental  of  water. 

3.  Value  as  an  Investment. — As  an  investment  irrigation 
works  are  not  always   successful.      There  should  be  a  ready 
market  for  the  products  of  irrigation,  and  the  value  of  land 
and  water  must  not  be  so  great  as  to  materially  reduce  the 
profits    derived    from   crops.     The    value    of  irrigation    as  an 
investment    is   especially  dependent  on  the  humidity  of   the 
climate.     In  the  semi-humid  region,  where  during  occasional 
seasons  the  rainfall  is  sufficient  to  mature  the  crops,  there  is 
little  or  no  demand  for  water  furnished  for  irrigation,  and  no 
profit  is  derived  from  its  sale.     In  the  arid  region,  where  crops 
cannot  be  raised  without  the  aid  of  irrigation,  the  demand  for 
water  is  constant.     In  the  northern  provinces  of  India  water  is 
in  constant  demand  for  irrigation  and  returns  excellent  profits. 
In  Bombay  and  other  places  where  the  demand   for  water  is 
intermittent,   because  the   rainfall   is    frequently   sufficient  to 
mature  crops,  the  construction  of  irrigation  works  has  usually 
resulted    in    financial   disaster.     Perhaps   the  most  important 
factor  bearing  on  this  subject  in  our  own  country  is  the  degree 
of  habitation.     Nearly  anywhere  that  a  good  market  can  be 
found   and  irrigation  is  essential  to  the   production  of  crops, 
fair  interest  can  be  obtained  on  money  invested  in  irrigation 
works.     Many  failures,  however,  have  occurred,  due  chiefly  to 
the  lack   of  population    and    consequent  lack  of  demand  for 
water.     Where    all  the  water  furnished  is  utilized  the  works 
almost  invariably  pay  fair  returns  on  the  investment. 

4.  Incidental  Values. — Not  only  is  the  direct  money  re- 
turn from  an  irrigation  investment  to  be  considered,  but  there 
are  several  incidental  means  whereby  profit  may  be  derived 
from  such  investments.     On  broad  principles  of  general  gov- 
ernment and   policy  the   construction  of  irrigation  works  is  of 
benefit  to  the  whole  country.     They  furnish  homes  and  agri- 
cultural pursuits  for  many  who  must  otherwise  be  idle  or  find 
less  substantial  support  in  other  ways.     Irrigation  adds  to  the 


COST  AND  RE  TURNS  OF  IRRIGATION. 


general  wealth  of  the  country  by  increasing  the  amount  of  its 
agricultural  products.  It  furnishes  excellent  investment  for 
capital  where  the  projects  are  well  designed.  It  results  in  the 
conversion  of  barren  and  desert  lands  into  delightful  homes, 
and  aids  in  the  general  development  of  the  other  resources  of 
the  region  in  which  it  is  practised,  as  mining,  lumbering,  graz- 
ing, etc.  One  of  the  great  advantages  of  irrigation  is  that  it 
becomes  practically  an  insurance  on  the  production  of  crops. 
Its  practice  may  not  be  necessary  in  the  semi-humid  or  humid 
regions,  but  even  there  occasional  droughts  occur  and  crops 
are  lost.  Where  an  irrigation  system  exists  in  such  cases,  it 
will  probably  be  called  into  requisition  once  or  twice  in  the 
course  of  a  year,  and  may  save  vast  sums  which  would  other- 
wise be  lost  by  the  destruction  of  crops. 

5.  Cost  and  Returns  of  Irrigation.— The  following  table 
compiled  from  the  reports  of  the  U.  S.  Census  of  1890  gives 
an  excellent  idea  of  the  extent  and  cost  of  irrigation,  and  of 
the  value  of  the  land  and  water  after  irrigation  has  been  pro- 
vided : 

TABLE  I. 

EXTENT    AND   COST    OF    IRRIGATION. 


States 
and 
Territories 
employing 
Irrigation. 

Crop 
Irrigated. 
Acres. 

11 

S 

C/J 

«*Ss 

m 

>   u   C 
<'-•' 

« 
fl 

5ua 

Average  Value  of 
Water  per  Acre 
as  estimated  by 
Irrigators. 

Average  Annual 
Cost  of  Water 
per  Acre. 

Average  Cost  of 
Preparing  Land 
for  Cultivation 
per  Acre. 

Average  Value  of 
Land  Irrigated 
per  Acre. 

Average  Value  of 
Products  from 
Irrigated  Land 
per  Acre. 

Total  U    S  

3,564,416 

67 

$8.15 

$26.00 

$0.99 

$12.12 

$8328 

$14.89 

Arizona 

65,821 
1,004,233 

890,735 
217,005 
350,582 
224,403 
9^745 
177,944 
263,473 
48,800 
229,6/6 

61 

73 
92 
50 
95 
192 

30 
56 
27 
47 
119 

7.07 
15.84 
7-15 
4-74 
4-63 
7.58 
5-58 
4.64 
10.55 
4.03 
3-62 

12.58 
52.28 
28.46 
13.18 
15.04 
24.60 
18.30 
15.48 
26.84 

13.15 
8.69 

1-55 
i  .60 

•79 
.80 

•95 
.84 
1-54 
•94 
.91 

•75 
.44 

8.60 
22.27 
9.72 

9-31 
8.29 

10-57 
11.71 

12.59 
14.85 
10.27 
8.23 

$48.68 
i  50  .  oo 
67.02 
46.50 
49-50 
41.00 
50.98 
57.00 
84.25 

50.00 
31.40 

$13.92 
19.00 
13.12 
12.93 
12.96 
12.^2 
12.  80 
13   90 
18.03 
17.09 
8.25 

California       .... 

Colorado  

Idaho         

Montana  

Nevada  

New  Mexico  
Oregon    . 

Utah  

Washington 

^Vvoming   

4  IN  TROD  UCTION. 

From  this  table  it  will  be  seen  that  while  the  average  first  cost 
of  water,  that  is,  the  cost  of  constructing  canals  to  bring  the 
water  to  the  land,  is  $8.15  per  acre,  the  average  value  of  water 
per  acre  as  estimated  by  the  owners  after  they  obtain  it  is 
$26.  This  shows  clearly  the  inherent  value  which  the  mere 
fact  of  possessing  the  water  gives  to  it.  In  other  words,  the 
water  is  so  scarce  and  valuable  of  itself  as  to  increase  by 
threefold  the  cost  of  making  it  available.  The  average  value 
of  the  land  before  irrigation  is  from  $2.50  to  $5  per  acre,  while 
the  same  land  after  a  water  supply  has  been  provided  is 
valued  at  $83.28  per  acre,  and  the  products  from  this  land  have 
an  average  value  of  $14.89  per  acre,  which  represents  an  unusu- 
ally large  interest  on  the  money  invested. 


PART   I. 

HYDROGRAPHY. 


CHAPTER    II. 
PRECIPITATION. 

6.  Relation  of  Rainfall  to  Irrigation. — In  a  region  where 
the  climate  and  soil  are  favorable  for  the  production  of  agri- 
cultural crops  the  necessity  of  irrigation  depends  wholly  on 
the  amount  of  rainfall.  The  necessity  of  irrigation  cannot  be 
judged,  however,  from  the  total  amount  of  precipitation  in  the 
year.  Where  the  precipitation  is  less  than  20  inches  per 
annum  in  the  United  States,  irrigation  is  generally  supposed  to 
be  necessary,  and  our  arid  region  is  usually  considered  as  includ- 
ing that  portion  of  the  country  where  the  annual  precipitation 
is  below  20  inches.  This,  however,  is  not  a  safe  gauge  in  all 
cases.  Thus  in  Italy,  where  the  annual  precipitation  averages 
perhaps  40  inches,  irrigation  is  necessary,  because  most  of 
this  occurs  during  the  winter  months  or  at  other  times  than 
in  the  agricultural  or  cropping  season.  In  India  the  rain- 
fall is  in  some  places  as  high  as  100  to  300  inches  per  annum. 
Yet  nearly  all  of  this  occurs  in  one  or  two  seasons  of  the  year, 
and  the  actual  rainfall  during  the  winter  months,  when  most 
of  the  cropping  is  done,  may  be  as  low  as  5  to  10  inches. 
Generally  speaking,  the  cropping  season  for  our  West  may  be 
taken  as  occurring  between  April  and  August  inclusive,  and 
these  are  among  the  dryest  months  in  the  year. 


O  PREC1PITA  TION. 

7.  General  Rainfall  Statistics.— Tables  II  and  III  show 
in  a  general    way  the  extent   of  precipitation   over   the    arid 
region.     From    them  it  will  be  seen   that    the  average  annual 
rainfall  over  the  northern  portion  of  the  Pacific  Coast  would 
be    sufficient    in    amount   for   the    production    of   crops,    pro- 
viding it   fell  during  the  irrigating  season.      There  is   also  a 
small    area   near    San    Diego,    and    one   on    the    headwaters 
of  the  Gila  and  Salt  rivers  in  Arizona,  where  the  annual  rain- 
fall is  apparently  sufficient  for  the  maturing  of  crops.     The 
amount   of    precipitation    is   greatly   influenced    by   altitude. 
Thus    in    the    same    latitude    in   the    region    between    Reno, 
Nevada,  and  San    Francisco,   California,  the  average   annual 
precipitation    in    the    bottom    of   the    Sacramento    Valley    is 
about   15   inches.      To  the  eastward  of  this  the  precipitation 
increases  in  amount  with  the  height  of    the  mountains  until 
along  their  summits  it  averages  from  50  to  60  inches.     Still 
further  east  it  decreases  with  the  diminishing  altitude  until  in 
Nevada  the  mean  precipitation  is  from  5  to  10  inches.     Every- 
where throughout  the  West  precipitation  in  the  high  mountains 
is  much  greater  than  in  the  adjacent  low  valley  lands.     As  a 
result  of  this,  while  the   rainfall  is  frequently  insufficient  to 
mature  crops  in  the  low  lands  and  valleys,  sufficient  precipita- 
tion occurs  in  the  mountains  to  furnish  an  abundant   supply 
for  the  perennial  discharge  of  streams  or  for  the  filling  of  stor- 
age reservoirs. 

8.  Rainfall  Distribution  in  Detail. — In   the   lower  Colo- 
rado and  Gila  river  valleys  in  Arizona  the  average  annual  pre- 
cipitation is  between  4  and  6  inches.     In  the  Gila  and  Salt 
river  valleys  in  the  neighborhood  of  Phoenix  it  is  between   10 
and   15    inches,  while  on  the  headwaters  of  these  streams  it 
averages  20 'inches.     In   Northern  Arizona  the  annual  average 
precipitation  is  about  10  inches,  most  of  which  occurs  in  win- 
ter.    During  the  summer  or  irrigating  months  the  precipitation 
is  from  I  to  3  inches  in  the  lower  Gila  and  Colorado  river  val- 
leys, from  3  to  5  inches  in  the  neighborhood  of   Phoenix  and 
Florence,  and  about  5  inches  in  Northern  Arizona. 

In  the  lower  Rio  Grande  and   Pecos  river  valleys  in  New 


RAINFALL   DISTRIBUTION.  J 

Mexico  the  average  annual  precipitation  is  10  inches.  Over 
the  remainder  of  the  agricultural  portion  of  the  Territory  it 
averages  about  15  inches.  In  winter  the  precipitation  is 
comparatively  low  in  the  valleys,  but  comparatively  high  in  the 
uplands.  In  the  summer  or  irrigating  months  it  ranges 
between  4  and  8  inches  in  the  Rio  grande  and  Pecos  valleys. 
In  California  in  the  Sacramento  valley  the  annual  average  pre- 
cipitation is  about  15  inches,  and  in  the  San  Joaquin  valley 
from  10  to  15  inches.  Over  the  agricultural  portions  of 
Southern  California  it  averages  about  the  same.  A  large  pro- 
portion of  this  rainfall  occurs  during  the  early  spring  months, 
but  in  the  latter  portion  of  the  irrigating  season  the  rainfall 
diminishes  very  rapidly,  averaging  from  May  till  October 
scarcely  two  inches  in  the  Sacramento  valley  and  less  than 
an  inch  in  the  San  Joaquin  valley  and  in  Southern  California. 
Over  the  plains  of  Western  Nevada  the  average  annual  pre- 
cipitation is  between  $  and  10  inches,  most  of  which  occurs  at 
periods  other  than  in  the  irrigating  season.  On  the  plains  of 
Utah  the  annual  average  precipitation  is  from  10  to  15  inches, 
while  the  precipitation  during  the  summer  months  is  but  an 
inch  or  two. 

In  the  upper  Missouri  and  Yellowstone  valleys  and  other 
principal  agricultural  portions  of  Montana  the  average  annual 
precipitation  is  from  12  to  20  inches,  of  which  about  5  inches 
falls  during  the  irrigating  season.  In  the  Snake  River  valley 
of  Idaho  the  average  annual  precipitation  is  about  10  inches, 
of  which  about  3  inches  falls  during  the  irrigating  season.  In 
the  Platte  and  Arkansas  valleys  of  Colorado  the  average  annual 
precipitation  is  about  15  inches,  of  which  from  7  to  10  inches 
fall  during  the  irrigating  season.  In  the  eastern  portion  of 
Colorado  on  the  plains  nearer  the  Kansas  line  the  precipita- 
tion is  a  little  less  than  this  and  about  the  same  as  in  the 
upper  Rio  Grande  valleys. 

9.  Great  Rainfalls. — One  of  the  important  considerations 
in  designing  irrigation  projects,  and  especially  storage  reservoirs, 
is  the  maximum  amount  of  rainfall  which  may  occur.  Great 
floods  are  the  immediate  result  either  of  the  sudden  melting 


8  PRECIPITATION. 

of  snow  in  the  mountains  or  of  heavy  and  protracted  rain- 
storms. In  most  of  the  river  valleys  just  considered  there  are 
periods  of  extreme  or  maximum  rainfall,  the  recurrence  and 
effect  of  which  are  worthy  of  note.  In  the  neighborhood  of 
Yuma,  Arizona,  the  average  annual  rainfall  is  about  3  inches, 
yet  in  the  last  week  of  February,  1891,  2\  inches  fell  in  24 
hours.  The  average  annual  rainfall  in  the  neighborhood  of 
San  Diego,  California,  is  about  12  inches,  yet  in  the  storms  of 
February,  1891,  13  inches  fell  in  23  hours  and  23  j-  inches  in  54 
hours.  In  the  neighborhood  of  Bear  Valley  reservoir  east  of 
Redlands,  California,  during  the  same  storm  17  inches  of  rain 
fell  in  24  hours.  Such  storms  as  these  may  be  very  destruc- 
tive both  to  crops  and  works.  The  average  annual  dis- 
charge of  Salt  River  in  Arizona  is  about  1000  second-feet,  and 
the  average  flood  discharge  is  perhaps  10,000  second-feet;  yet, 
as  the  result  of  a  sudden  rainstorm  of  unusual  violence  which 
occurred  in  the  spring  of  1891,  this  river  increased  to  a  flood 
discharge  of  140,000  second-feet,  and  in  the  spring  of  1892,  as 
the  result  of  a  still  greater  cloud-burst,  its  discharge  reached 
the  enormous  figure  of  nearly  350,000  second-feet.  Over  cer- 
tain portions  of  the  western  region  these  sudden  cloud-bursts 
are  of  not  uncommon  occurrence  and  must  be  provided  for  in 
the  construction  of  works. 

10.  Suddenness  of  Great  Storms. — Statistics  showing 
the  rainfall  in  24  hours  are  often  insufficient  to  give  a  safe 
and  correct  estimate  of  the  suddenness  and  danger  of  floods 
resulting  from  great  storms.  The  greatest  and  most  sudden 
storm  on  record  is  probably  that  which  occurred  on  the 
line  of  the  Lower  Ganges  canal  in  the  Northwest  Prov- 
inces of  India.  On  the  J_3th_of  September,  1884,  16  inches 
fell;  on  October  the  1st  22  inches,  on  the  2d  22|,  on  the  3d  18 
inches,  and  on  the  4th  17^  inches  of  rain  fell.  In  some  cases 
and  at  some  times  the  precipitation  was  as  high  as  5  inches  per 
hour.  In  some  of  the  cloud-bursts  in  our  own  West  it  is  not 
unlikely  that  the  precipitation  has  reached  from  3  to  5  inches 
per  hour.  Such  storms  as  these  do  far  greater  damage  than 
protracted  storms  of  less  violence. 


PRECIPITATION  ON  RIVER   BASINS.  9 

ii.  Precipitation  on  River  Basins.— The  following  table 
of  rainfall  on  a  few  of  the  principal  river  basins  of  the  West 
shows  very  clearly  the  variation  in  the  amount  of  precipita- 
tion at  different  altitudes  : 

TABLE  II. 

PRECIPITATION    BY    RIVER    BASINS. 


Station. 


Altitude. 
Feet. 


Mean  Annual 

Precipitation. 

Inches. 


Rio  GRANDE  RIVER  : 

Summit,  Colorado 11300  29.00 

Fort  Lewis,  Colorado 8500  I7-I9 

Fort  Garland,      "         i  7937  I2-74 

Saguache,             "         '774°  42.60 

Santa  Fe,  New  Mexico 7026  14.69 

Fort  Wingate,  New  Mexico 6822  14 . 71 

Las  Vegas,                                6418  22.08 

Albuquerque,                            5032  7 .19 

Socorro,                             "     ;  4560  8.01 

Deming,                            "     |  4315  8.95 

GILA  RIVER: 

Fort  Bayard,  New  Mexico I  6022  14.72 

Prescott,  Arizona 5389  17.06 

Fort  Apache,  Arizona 5050  21 .04 

Fort  Grant,            "       4914  16.65 

Phoenix,                 "       j  1068  7 . 38 

Texas  Hill,            "       |  353  3.47 

Yuma,                    "       I  141  2.81 

PLATTE  RIVER  : 

Pike's  Peak,  Colorado I4T34  28.65 

Fort  Saunders,  Wyoming 7180  12.92 

Fort  Fred  Steele,       "        6850  11.03 

Cheyenne,                   "        6105  11.32 

Colorado  Springs,  Colorado 6010  14 . 79 

Denver,                            " 5241  14-32 

Fort  Morgan,                  "       4500  8.08 

MISSOURI  RIVER  : 

Virginia,  Montana 5480  16.00 

Fort  Ellis,        "       4754  19-60 

Helena,            "       4266  14.26 

Fort  Shaw,       " 2550  10.22 

Poplar,             "       1955  I0-50 


12.  Rainfall  Statistics  by  States.— Table  III  gives  the 
average  annual  precipitation,  and  the  precipitation  during  the 
irrigating  season,  from  April  to  August  inclusive,  for  various 
places  in  each  of  the  Western  States  : 


10 


PRECIPITA  TION. 


TABLE  III. 

PRECIPITATION    BY   STATES. 


Locality. 


Altitude. 
Feet. 


Mean  Annual 

Precipitation. 

Inches. 


Mean  Precipi- 
tation, April 
to  August. 
Inches. 


ARIZONA  : 

Fort  Apache 5050 

Holbrook 504  7 

Casa  Grande 1398 

Phoenix 1068 

Texas  Hill 355 

Prescott 5389 

NEW  MEXICO  : 

Springer 57°6 

Las  Vegas 6418 

Albuquerque 5026 

Santa  Fe 7026 

Fort  Wingate 6822 

Socorro 4565 

Deming 4327 

CALIFORNIA  : 

Yreka 2635 

Fort  Bid  well 4640 

Redding 556 

Oroville    188 

-    Bowman  Dam 54°° 

Summit 7017 

Placerville 2110 

Sacramento 64 

San  Jose 94 

Merced 171 

Fresno 328 

Visalia 348 

San  Bernardino 950 

Banning 2317 

Los  Angeles 330 

San  Diego 93 

Yuma 276 

NEVADA : 

Reno 4497 

Winnemucca 4358 

Palisade 4840 

Fort  Churchill 4284 

Carson 4628 

Pioche 61 10 

RADO: 

"Jreeley 4750 

*3reckenridge 9524 

'  eadville 10200 

'ike's  Peak 14^34 

Canyon  City 4700 

Pueblo 4753 

Fort  Lyon 4000 

Monte  Vista 7765 

Trinidad 6070 

Denver 5241 


21.04 
9.29 
4.28 

7-38 

3-47 

17.06 

11.82 
22.08 

7.19 
14.68 
14.71 
10.31 

8-95 

16.34 
20.84 
34.60 

25.14 
71.21 
43-56 
45-17 
19.80 
14.52 
10.30 
9.02 
8.84 
17.  16 

14-39 

18.31 

9.86 

3.16 

5-17 
8.61 
8.42 

5-3i 
11.25 
ii.  19 


28.25 
11.56 
28.65 
11.52 

9.87 
11.07 

6.91 

21  .6l 
T4-32 


10.27 

3- 68 
1.32 
2.27 
.66 
7-94 

8.86 
12.70 
4.22 
8.32 
6.97 
3.8? 
3-90 

3-33 
4.54 
5.61 
3.48 


8.26 

2-73 
2.08 

1-73 
i.  80 
1.86 

2-37 
i. 80 
1.81 
2-47 
i. 06 


0.71 
2.70 
2.17 
1.70 
2.05 
4.41 


9. 16 


7.01 
7.10 
8.15 
4.18 
15.06 
9.00 


GAUGING   RAINFALL. 
TABLE  III. — Continued. 


I  1 


Locality. 

Altitude. 
Feet. 

Mean  Annual 
Precipitation. 
Inches. 

Mean  Precipi- 
tation, April 
to  August. 
Inches. 

UTAH: 
Ogden               .... 

414.O 

ja    *{\ 

Salt  Lake  

4-3C4 

16  85 

4.  12 

A     ,,A 

Nephi 

c  e  co 

18  IQ 

St    George     .              

2880 

6    7J 

7.4° 

IDAHO  : 
Eagle  Rock 

478l 

18  67 

•  j* 

4    Ark 

Boise 

1108 

14    7^ 

.09 

Lewiston.     .  .        .      .  .      .        ... 

18  25 

.  II 

Fort  Hall 

17     5  T 

•55 
6/1/1 

WYOMING  : 
Cheyenne     

6105 

*/  •  31 

I    72 

•44 

Fort  McKinnev 

•  55 

MONTANA  : 
Fort  Benton 

2730 

1  7    7O 

4-45 

Miles  City  

4-772 

12    OO 

•45 

See 

Helena  

4266 

14   26 

•  55 

4d.8 

Fort  Shaw 

2CCQ 

IO    22 

•  ^5 

13.  Gauging  Rainfall. — The  common  rain-gauge  or  plu- 
viometer generally  employed  in  this  country  in  the  measure- 
ment of  precipitation  is  illustrated  in  Fig.  I.  It  consists  of 


FIG.  i. — RAIN-GAUGB. 

three  parts,  the  collector^,  the  receiver  B,  and  the  overflow  at- 
tachment C.  A  measuring-rod  graduated  to  inches  and  tenths  is 
furnished  with  each  gauge  and  is  used  in  measuring  the  depth 
of  water.  This  gauge  should  be  placed  in  an  open  space,  prefer- 
ably over  grass  sod,  and,  to  obtain  a  free  exposure  to  the  rain, 


1 2  PRE  CIPI TA  TION. 

should  be  at  least  30  feet  from  any  building  or  obstruction.  It 
should  be  enclosed  in  a  close-fitting  box  and  sunk  into  the 
ground  to  such  a  depth  that  the  upper  rim  of  the  gauge  shall  be 
about  one  foot  above  the  surface,  and  care  should  be  taken  to 
maintain  it  in  a  horizontal  position.  The  sectional  area  of  the 
receiver  being  only.i  of  the  area  of  the  collector,  the  depth  of 
water  measured  is  ten  times  the  true  rainfall. 

In  the  measurement  of  snowfall  the  funnel  and  receiver 
should  be  removed  and  only  the  overflow  attachment  used  as 
the  collecting  vessel.  It  should  be  set  as  in  the  case  of  rain- 
fall and  the  snow  should  be  melted  after  being  collected. 
Where  the  wind  is  blowing  hard  it  is  advisable  to  measure  the 
snow  in  a  different  manner.  After  the  snow  has  ceased  to  fall 
a  spot  should  be  selected  where  it  has  an  average  depth. 
The  overflow  attachment  is  inverted  and  lowered  until  the  rim 
has  reached  the  full  depth  of  the  newly-fallen  snow,  when  a 
piece  of  flat  tin  or  other  material  is  slipped  under  the  rim  and 
the  gauge  lifted  and  the  snow  melted  as  before. 

14.  Works  of  Reference. — For  fuller  information  consult : 

FANNING,  J.  T.     A  treatise  on  Hydraulic  and  Water  Supply  Engineer- 
ing.    D.  Van  Nostrand  &  Co.,  New  York,  1890. 
FITZGERALD,   DESMOND.     Maximum  Rates  of  Rainfall.    Transactions 

Am.  Soc.  of  C.  E.  1889,  vol.  21. 
GREELY,  Gen.   A.  W.,  and  GLASSFORD,  Lieut.  W.  A.     Irrigation  and 

Water  Storage  in  the  Arid  Regions.     Sist  Congress,  House  of  Rep. 

Ex.  Doc.  No.  287.     Washington,  D.  C.,  1891. 
GREELY,  Gen.  A.  W.     Report  of  Rainfall.     $oth  Congress,  Senate  Ex. 

Doc.  No.  91.     Washington,  D.  C.,  1888. 
NEWELL,  F.  H.     Part  II  of  nth,   i2th,  and    i3th  Annual   Reports  of 

U.  S.  Geological  Survey.     Government  Printing  Office,  Washington, 

D.C.,  1890,  '91,  '92. 


CHAPTER  III. 
EVAPORATION  AND  ABSORPTION. 

15.  Evaporation  Phenomena. — The  rapidity  with  which 
water,  snow  and   ice  are  converted   into  vapor  is  dependent 
upon  the  relative  temperatures  of  the  water  and  atmosphere 
and  upon  the  amount  of  motion  in  the  latter.     Evaporation 
is  greatest  when  the  atmosphere  is  dryest,  when  the  water  is 
warm  and  a  brisk  wind  is  blowing.     It  is  least  when  the  atmos- 
phere is  moist,  the  air  quiet  and  the  temperature  of  the  water 
low.     In   summer  the  cool  surfaces  of  deep  waters  condense 
moisture  from  the  warm  air  passing  across  them  and  thus  gain 
in  moisture  when  they  are  supposed  to  be  evaporating.     When 
the  reverse  conditions  exist  in  the  atmosphere  and  the  winds 
are  blowing  briskly  across  the  water  the  resultant  wave-motion 
increases  the  agitation  of  the  body  and  permits  its  vapors  to 
escape  freely  into  the  large  volumes  of  unsaturated  air  which 
are   rapidly   presented    in    succession    to    attract    its    vapors. 
Evaporation  is  constantly  taking  place  at  a  rate  due  to  the 
temperature  of  the  surface  and  condensation  is  likewise  going 
on  from  the  vapors  existing  in  the  atmosphere,  the  difference 
between  the  two  being  the  rate  of  evaporation. 

From  the  above  it  will  be  seen  that  evaporation  should  be 
greatest  in  amount  in  the  desert  regions  of  the  Southwest  and 
least  in  the  high  mountains.  Tables  IV  and  V  show  this  to 
be  the  case  and  that  in  the  same  latitude  evaporation  differs 
greatly  in  amount  according  to  the  altitude. 

16.  Measurement    of    Evaporation.  —  Two     or    three 
methods  have  been  devised  for  measuring   evaporation   none 

13 


14  EVAPORATION  AND   ABSORPTION. 

of  which  are  wholly  satisfactory.  Elaborate  and  expensive 
apparatus  has  been  employed  in  evaporation  measurements 
made  by  Mr.  Desmond  Fitzgerald,  chief  engineer  of  the 
Boston  Water  Works  ;  by  Mr.  Charles  Greeves  of  England,  and 
others.  A  simple  apparatus  and  one  which  is  as  successful  as 
most  of  the  more  elaborate  contrivances  is  that  employed  by 
the  U.  S.  Geological  Survey.  It  consists  of  a  pan,  Fig.  2,  so 


FlG.  2. — EVAPORATING-PAN. 

placed  that  the  contained  water  has  as  nearly  as  possible  the 
same  temperature  and  exposure  as  that  of  the  body  of  water 
the  evaporation  from  which  is  to  be  measured.  This  evapora- 
ting pan  is  of  galvanized  iron  3  feet  square  and  10  inches  deep, 
and  is  immersed  in  water  and  kept  from  sinking  by  means  of 


AMOUNT  OF  EVAPORATION.  15 

floats  of  wood  or  hollow  metal.  It  should  be  placed  in  the 
canal,  lake,  or  other  body  the  evaporation  of  which  it  is  in- 
tended to  measure  in  such  position  as  to  be  exposed  as  nearly 
as  possible  to  its  average  wind  movements.  The  pan  must  be 
filled  to  within  3  or  4  inches  of  the  top  in  order  that  the  waves 
produced  by  the  wind  shall  not  cause  the  water  to  slop  over,  and 
it  should  float  with  it  srim  several  inches  above  the  surrounding 
surface,  so  that  waves  from  this  shall  not  enter  the  pan.  The 
device  for  measuring  the  evaporation  consists  of  a  small  brass 
scale  hung  in  the  centre  of  the  pan.  The  graduations  are  on  a 
series  of  inclined  crossbars  so  proportioned  that  the  vertical 
heights  are  greatly  exaggerated,  thus  permitting  a  small  rise  or 
fall,  say  of  a  tenth  of  an  inch,  to  cause  the  water  surface  to 
advance  or  retreat  on  the  scale  .3  of  an  inch.  By  this  device, 
multiplying  the  vertical  scale  by  three,  it  is  possible  to  read 
to  .01  of  an  inch. 

In  1888  a  series  of  observations  were  made  with  the 
Piche  evaporometer  by  Mr.  T.  Russell  of  the  U.  S.  Signal 
Service  to  ascertain  the  amount  of  evaporation  in  the  West. 
While  it  is  probable  that  results  obtained  with  this  instrument 
are  not  particularly  accurate,  comparisons  of  these  results  with 
those  obtained  by  other  methods  in  similar  localities  show  such 
slight  discrepancies  that  they  may  be  considered  of  value  until 
superseded  by  results  obtained  by  other  and  better  methods. 
Observations  were  made  with  this  instrument  in  wind  velocities 
varying  from  10  to  30  miles  per  hour,  from  which  it  was  dis- 
covered that  with  a  velocity  of  5  miles  an  hour  the  evaporation 
was  2.2  times  that  from  one  in  quiet  air;  10  miles  per  hour 
3.8  times  ;  15  miles  4.9  ;  20  miles  5.7  times;  25  miles  6.1,  and 
30  miles  6.3  times. 

17.  Amount  of  Evaporation. — In  Table  IV  is  given  the 
amount  of  evaporation  by  months  in  the  year  1888  in  various 
sections  of  the  West  as  derived  from  experiments  with  the 
Piche  apparatus. 

As  in  the  case  of  precipitation,  evaporation  decreases  with 
the  altitude  because  of  the  diminished  temperature  in  high 
mountains.  Experiments  were  made  to  determine  the  amount 


1 6  'EVAPORATION  AND  ABSORPTION. 

TABLE  IV. 

DEPTH    OF   EVAPORATION,  IN    INCHES  PER  MONTH,  IN  1887-88. 


Stations  and  Districts. 

3  " 

&  00 

«     H 

fl 

=  8 

-  00 

>jf 

j| 

—  » 

fi 

i- 

1? 

< 

'    IX 

a* 

r 

I- 

rcS- 

r 

1 

NORTHERN  SLOPE  : 
Fort  Assiuiboine  
Fort  Custer               

0.8 
o  6 

1.2 

I  .2 

J-3 

3-1 

5-4 

J'S 

4-2 

4.9 

6.8 

0  6 

\\ 

4.8 
6.1 

3-5 
3-4 

2-5 

2.9 

i.i 
1.5 

39-5 
52.0 

3-  3 

3.2 

1  6 

6.8 

i  fi 

1  R 

9  R 

2.O 

i.i 

35.8 

Helena 

i  fi 

o  8 

o  R 

2.7 

4.9 

5.7 

6  o 

4.4 

2.  5 

I  .7 

0.7 

OC.A 

Cheyenne  
North  Platte                   .    ... 

3-3 
o  8 

5'5 

4.0 
i  8 

8.2 

5-4 

5-2 

3-9 

0.4 
6.9 

8.0 

6  o 

7-7 

8.6 
3-7 

5.8 

->  R 

6.; 
2.3 

3-5 
i  .  i 

76.5 

41  •  3 

MIDDLE  SLOPE: 
Colorado  Springs  
Denver  ....        

?•« 

3-3 
3-7 

4-1 

3-5 

6-7 

7  6 

r» 

4-3 
0.5 

6.7 

R    7 

7.2 
8  S 

6.8 

6    T 

46 
4-9 

4-2 
4-2 

2.9 
3-  * 

59-4 
69.0 

Pike's  Peak               

2.  1 

T    8 

i  .9 

3.0 

4.0 

3-° 

2.3 

7    R 

i  .0 

26.8 

2    8 

i  8 

1    8 

4-3 

T     R 

47.2 

Dodge  City  
Fort  Elliott  
SOUTHERN  SLOPE  : 
Fort  Sill 

i-4 

i  .3 

i  6 

2.4 
1.9 

2.8 
3-2 

2    6 

4-1 

5-i 
,  8 

J:l 

5-4 

7-4 

8.2 

8.3 
7.6 

A.   8 

6.6 

6.2 

5-5 
5-4 

5-2 

4-7 

4.2 

4-2 

2.1 
2.2 

54-6 
55-4 

46  i 

Abilene  

i   R 

3-  T 

5.0 

r    8 

9-  5 

7-5 

6  f 

3-4 

I  .  7 

M-4 

Fort  Davis  

5-4 

5-7 

6.7 

8-5 

i  .0 

2.O 

11.4 

9.0 

5-9 

S-2 

5-7 
o  6 

4-9 
o  g 

96.4 

SOUTHERN  PLATEAU  : 
El  Paso 

6  o 

8  4 

5  6 

1  6 

82  o 

Santa  Fe*  

6  8 

8  8 

0.8 

6  6 

6  , 

5-7 

79.8 

n     f 

6  8 

6  T 

2    6 

fie    c 

Ty'« 

Prescott 

6    2 

8  i 

6  6 

6  j 

T   6 

Yuma  
Keeler               ... 

4-4 

5-2 

6.6 
6  3 

9.6 

9  6 

12.6 

ii  .0 

12    8 

1O.2 

8.2 

10  6 

8.2 

R  R 

5-5 

;•« 

95-  7 

MIDDLE  PLATEAU  : 
Fort  Bidwell 

o  8 

8  8 

R 

1  6 

48  o 

Winnemucca  

O.Q 

2. 

6  ? 

g. 

Q. 

10.  T 

ii  .5 

12. 

9.9 

6  6 

3.7 

i  « 

83.9 

Salt  Lake  City 

T    9 

g 

8    Q 

Q    6 

6    r 

Montrose     

i  8 

6 

R 

60 

0.4 

2  .O 

68.3 

Fort  Bridger 

6  =; 

6 

e    fi 

56  i 

NORTHERN  PLATEAU: 
Boise  City 

6 

6 

<s  <= 

i  8 

Spokane  Fails  
Walla  Walla  
NORTH  PACIFIC  COAST: 

0.7 
1.  1 

i- 
2.9 

3: 

4- 
6. 

5- 
7- 

4-4 
5-7 

7-7 

9-9 

. 
7- 

3-8 
5-i 

2.5 
3-4 

I  & 

1.7 

i.£ 

I   .£ 

2.i 

42.  a 

57.7 

Olympia  
Tatoosh  Island 

1.3 

1.2 

i. 

2. 

4- 

3-: 

I    £ 

3-2 

3- 

•2.1 

1.5 

i  6 

i.i 

I.I 

26.8 

18  i 

Roseburg  
MIDDLE  PACIFIC  COAST: 
Red  Bluffs  
Sacramento 

1.5 

3-c 

1.6 
4.6 

2. 

5- 

3- 
6. 

4- 
7- 

3-: 

6.c 

c    ( 

5-4 

II  .C 

4 
10. 

5-c 

10. 

6 

3-2 

IO.  S 

i.j 

5-< 

i.e 
3-< 

39-a 
84.8 

SOUTH  PACIFIC  COAST: 
Fresno            

2  g 

o 

g 

6  ' 

65  8 

-,  ( 

San  Diego     

»:i 

3- 

of  evaporation  in  different  portions  of  the  West  by  the  hydrog- 
raphers  of  the  U.  S.  Geological  Survey.  These  were  made 
with  the  evaporating  pan,  and  the  results  are  probably  more 
reliable  than  those  obtained  with  the  Piche  instrument.  These 
experiments  were  unfortunately  conducted  for  a  relatively 
short  space  of  time.  From  a  comparison  of  a  few  of  these 


EVAPORATION  FROM   SNOW  AND  EARTH. 


which  are  complete  it  will  be  seen  that  they  agree  well  with 
the  results  given  by  Mr.  Russell's  observations. 

TABLE  V. 

DEPTH   OF    EVAPORATION    PER   MONTH,    IN    INCHES. 


I 

Place. 

Annual. 

e 

3 

1 

March. 

a 
< 

>» 

CO 

| 

£, 
"B 
i—  » 

} 

a 

1 

S 

i 

1 

1889 
1890 
1889 

1889 

,889 
1889 

1890 
1891 

1889 
1889 
1889 
1890 

1889 

1889 

,889 

1890 
1891 

1889 

1890 
1891 
1890 
1889 
1890 
1890 
1890 
1890 

1890 
1890 

Bozeman,  Mont      

3-4 

4-5 

5-3 

i.9 

.... 

2    6 

Great  Falls,  "     

Springdale,   "     

6.8 

i:i 

3-i 

29 

.... 

Hogan,           "     

(  Fort  Douglas,   near   )  
•<         Salt   Lake   City,   >... 

7   6 

10.5 

M 

I.O 

)          Utah                          f.... 
Nephi  and  Provo               .  .   . 

36.4 

.... 

3-2 

4.8 

5-2 

3-9 
8.1 

7-6 
5-o 
7-9 

6J 
4.6 
8.6 

5-2 

!:! 

2.5 

3-3 
4.2 
o  6 

i-4 

2-5 

2.2 

Cherry  Creek,  Col  

Canyon  City,     "    

3-8 

4.8 

52 

7-3 

6.0 

Lamar,  Col  

Embudo,  New  Mexico  

3-o 

2.9 

3  6 

4.0 

10.9 
io  8 

10.7 

9.6 
9  6 

II.4 

7    6 

9-2 

6.8 

4.6 

2-9 

iFort   Bliss,   near  El   \  

Ro  T 

2.O 

2.O 

7.0 

Paso,  Texas  f  " 

empe,  Ariz  

6  4 

r    R 

e    g 

I  fi 

5-8 

5-2 

{.6 

3-2 

U                         U 

85.5 

3-9 

3-6 

11 

J:: 

"•5 

13-5 

M 

1.8 

2.5 

»  R 

7.2 

8-5 

7.2 

7-i 

4-3 

Bloods   Cal              

Tuolumne  Mead,  Cal  

rto 

18.  Evaporation  from  Snow  and  Ice. — From  some   ex- 
periments conducted  at  the  Boston  Water  Works  the  amount  of 
evaporation  from  snow  and  ice  was  found  to  be  greater  than  is 
generally  believed.     From  snow  it  amounted  to  about  .02  of 
an   inch   per  day,  or  nearly  2\  inches  in  an  ordinary  season. 
From  ice  it  amounted  to  .06  inch  per  day,  or  about  7  inches 
in  an  ordinary  season.     The  evaporation  from  snow  is  greater 
than  this  in  the  arid  regions  of  the  West,  especially  on  barren 
mountain-tops  such  as  those  in  Arizona,  Nevada,  and  Utah, 
where  they  are  exposed  to  the  wind  and  the  bright  sunshine. 

19.  Evaporation  from  Earth. — The  amount  of  evapora- 
tion from  earth  in  the  West  is  a  doubtful  quantity.     The  most 
important  experiments  bearing  on  this  were  made  in  England 
between    1844   and    1875.     From    these    it   appears   that   the 
amount  of  evaporation  from  ordinary  soil  is  about  the  same 


1 8  EVAPORATION  AND  ABSORPTION. 

as  that  from  water,  sometimes  exceeding  it  a  little  and  some- 
times being  a  trifle  less,  though  generally  averaging  about  3 
inches  less  than  the  corresponding  evaporation  from  water  sur- 
faces. The  evaporation  from  sandy  surfaces  was  found  to  be 
only  about  one-fourth  to  one-fifth  that  from  water.  Thus  in 
the  observations  of  1873,  where  the.  mean  evaporation  from 
water  was  20.4  inches,  that  from  earth  was  19.7  inches  and 
from  sand  3.7  inches. 

20.  Effect    of  Evaporation  on  Water    Storage.— The 
value  of  water  storage    for  irrigation  in  the  West  is  realized 
chiefly  between    May  and   August  inclusive.     The  only   loss 
due  to    evaporation    which    practically  affects  the  amount  of 
storage  water  is  that  occurring  during  these  months.     Little 
or  no  rain  falls  in  the  arid  region  during  this  period,  so  that 
comparatively  little   of  the  loss  of  evaporation  is  replaced  by 
rain.    As  an  example,  take  Central  California,  where  the  aver- 
age rainfall  during  these  months  amounts  to  a  trifle  less  than 
I  inch.     The  evaporation  during  the  same  period  amounts  to 
about  21  inches.     The  total  resultant  deficiency  chargeable  to 
evaporation  is  about  20  inches. 

21.  Percolation  and  its  Amount. — The  losses  due  to  per- 
colation in  canals  and  storage  reservoirs  are  very  considerable, 
and  added  to  those  due  to  evaporation  they  increase  the  total 
loss  by  from  25  to  100  per  cent  according  to  the  character  of 
the  soil.     It  is  difficult  to  ascertain  the  losses  due  to  percola- 
tion alone.     For  this  reason  it  is  desirable  to  consider  losses 
from  percolation  and  evaporation  together  and  include  them 
under  the  joint  head  of  "  absorption." 

From  the  experiments  previously  alluded  to  which  were  con- 
ducted by  Mr.  Greaves  in  England,  it  was  found  that  while  the 
evaporation  from  earth  during  the  period  of  23  years  was  73.4 
per  cent  of  the  rainfall,  the  percolation  was  but  26.6  per  cent. 
From  sand  this  percentage  was  nearly  reversed,  the  loss  by 
percolation  being  about  30  inches,  while  the  loss  by  evaporation 
was  but  7  inches.  There  was  no  loss  from  percolation  at  all  for 
several  consecutive  months.  As  an  average  year  take  that 
of  1872,  when  the  rainfall  amounted  to  23.8  inches  and  the 


AMOUNT  OF  ABSORPTION.  19 

evaporation  from  water  20.4  inches,  the  losses  by  percolation 
amounted  to  4  inches  in  earth  and  20.1  inches  in  sand.  From 
observations  and  experiments  made  in  Bavaria  it  appeared  that 
in  the  warm  summer  months  whereas  the  depth  of  percola- 
tion on  open  bare  ground  was  n  per  cent  of  the  rain- 
fall, in  forests  it  amounted  to  as  high  as  36  per  cent  of  the 
rainfall.  In  our  West  these  quantities  will  be  materially  differ- 
ent. The  amount  of  rainfall  is  relatively  small  on  the  ordi- 
nary mountain  catchment  basin.  The  slopes  are  steep  and  gen- 
erally rocky.  As  a  result  of  this  the  percentage  of  percolation 
will  be  low,  the  amount  of  runoff  being  relatively  higher. 
Where  there  are  dense  forests,  the  soil  beneath  which  is  covered 
with  a  depth  of  litter,  or  where  the  slopes  are  low,  the  per- 
centage of  percolation  will  be  relatively  high. 

22.  Absorption. — As  here  considered,  absorption  is  the 
resultant  or  total  loss  due  to  the  combined  action  of  evapora- 
tion and  percolation.  From  experiments  made  in  India,  where 
the  climate  is  somewhat  similar  to  our  western  country,  it  was 
found  that  the  loss  by  evaporation  on  a  canal  of  about  30  miles 
in  length  would  be  a  little  over  2.5  second-feet,  or  about  5  per 
cent  of  the  probable  discharge.  As  this  amount  is  compara- 
tively small,  it  appears  that  the  greater  portion  of  the  loss  is 
from  percolation.  Mr.  Beresford  argues  that  the  losses  by 
percolation  are  due  to  capillary  attraction  and  the  action  of 
gravity.  The  latter  takes  place  only  through  coarse  sand  or 
gravel,  while  the  former  is  a  more  complicated  process  acting 
where  the  particles  are  fine  and  in  close  contact  one  with  the 
other.  Capillary  attraction  stops  where  the  absorbing  medium 
is  limited,  for  as  soon  as  water  which  has  been  carried  by  its 
action  through  a  bank  reaches  the  outer  surface,  percolation 
ceases  and  evaporation  comes  into  play.  It  is  for  this  reason 
that  banks  of  sand  even  when  well  rammed  will  retain  water. 
The  more  extensive  the  absorbing  medium  the  greater  the 
losses  from  this  cause ;  but  if  its  extent  be  limited  by  a  bed  of 
clay  placed  under  either  the  reservoir  or  canal  in  which  per- 
colation occurs,  then  the  losses  due  to  this  cause  are  rapidly 
diminished  in  quantity.  The  layer  next  the 'wetted  perimeter 


20  EVAPORATION  AND  ABSORPTION. 

limits  the  quantity  absorbed,  and  the  greater  its  area  the  more 
will  it  pass  through  to  the  still  greater  area  of  the  next  layer  ; 
hence  percolation  varies  as  the  wetted  perimeter. 

23.  Amount  of  Absorption  in  Reservoirs  and  Canals. 
— The  volume  of  this  is  very  difficult  to  ascertain  and  varies 
greatly  with  soil  and  climate.     If  the  bottom  of  the  reservoir  is 
composed  of  sandy  soil,  the  losses  from  percolation  and  evapo- 
ration combined -will  be  about  double  those  from  the  former 
alone.     Whereas,  if  the  bottom  of  the  reservoir  be  of  clayey 
material,  or  if  the  reservoir  be  old  and  the  percolation  limited 
by  the  sediment  deposited  on  its  bottom,  this  loss   may  be 
considerably  less  than  that  of  evapoiation. 

On  a  moderate-sized  canal  in  India  the  total  losses  due  to 
absorption  have  been  found  to  amount  to  about  one  second-foot 
per  linear  mile.  In  new  canals  these  losses  are  greatest.  If 
the  soil  is  sandy,  the  losses  on  new  canals  may  amount  for  long 
lines  to  from  40  to  60  per  cent  of  the  volume  entering  the 
head.  In  shorter  canals  the  percentage  of  loss  will  be  propor- 
tionately decreased,  though  they  will  rarely  fall  below  30  per 
cent  in  new  canals  of  moderate  length.  As  the  canal  increases 
in  age  the  silt  carried  in  suspension  will  be  deposited  on  its 
banks  and  bottom,  thus  filling  up  the  interstices  and  diminish- 
ing the  loss.  In  old  canals  with  lengths  varying  between  30 
and  40  miles  the  loss  may  be  as  low  as  12  per  cent  in  favor- 
able soil,  though  in  general  for  canals  of  average  length  the 
loss  will  be  about  20  to  25  per  cent  of  the  volume  entering 
the  head.  On  the  Ganges  Canal  in  India,  the  length  of  which 
is  several  hundred  miles,  the  losses  in  some  years  have  been  as 
high  as  70  per  cent. 

24.  Prevention  of  Percolation. — An  excellent  method  for 
the  reduction  of  the  loss  by  percolation  is  that  recommended 
by  Mr.  J.  S.  Beresford  of  India,  who   advises  that  pulverized 
dry  clay  be  thrown  into  the  canals  near  their  headgates.     This 
will  be  carried  long  distances  and  deposited  on  the  sides  and 
bottom   of  the  canal,   forming  a  silt   berme.     The  losses  by 
absorption   are  greatly  increased  by  giving  the  canal  a  bad 
cross-section.     Thus  depressions  along  the  line  of  a  new  canal 


SEEPAGE    WATER.  21 

are  often  utilized  to  cheapen  construction  by  building  up  a  bank 
on*  the  lower  side  only,  thus  allowing  the  water  to  spread  and 
consequently  increasing  the  absorption.  The  least  possible 
wetted  perimeter  and  the  least  surface  exposed  to  the  atmo- 
sphere will  cause  the  least  loss  from  this  cause. 

25.  Seepage  Water. — In  many  instances  where  canals  and 
reservoirs  are  bordered  by  steep  hillsides  the  amount  of  water 
lost  may  prove  to  be  much  less  than  would  be  expected.  This 
is  due  to  the  fact  that  large  amounts  of  seepage  water  may 
enter  the  canal  or  reservoir  from  the  surrounding  country  and 
thus  replenish  to  a  large  extent  the  losses  from  absorption. 

Before  irrigation  becomes  universal  in  any  locality  it  is  fre- 
quently impossible  to  derive  any  water  from  wells.  The  sub- 
surface water  level  may  be  situated  at  a  great  depth  below 
the  surface.  After  irrigation  has  been  practised  for  some  time, 
however,  the  soil  becomes  filled  with  water  and  the  subsurface 
level  rises  so  that  shallow  wells  often  yield  persistent  supplies. 
In  portions  of  California,  especially  in  the  neighborhood  of 
Fresno  where  the  subsurface  water  level  was  originally  from 
60  to  80  feet  below  the  surface,  wells  10  and  15  feet  in  depth 
now  receive  constant  supplies,  the  result  of  seepage  from  the 
canals.  Water  used  in  irrigating  is  in  large  part  returned  to 
the  drainage  channels  and  can  be  again  diverted  for  irrigation. 
On  the  Cache  la  Poudre  Creek  in  Colorado  experiments  made 
in  1889  showed  that  while  the  original  discharge  in  the  canyon 
was  127.6  second-feet,  the  volume  at  a  point  considerably 
lower  down  on  the  stream  had  increased  to  214.5  second-feet 
after  supplying  fifteen  canals  and  without  receiving  additional 
naturald  rainage  ;  an  addition  of  more  than  two-thirds  of 
the  original  volume,  available  to  supply  canals  lower  down. 
Measurement  of  the  volume  of  water  in  the  Sweetwater  reser- 
voir in  Southern  California  shows  that  after  water  ceases  to  be 
drawn  out  of  the  reservoir  in  the  fall,  it  begins  to  fill  up  while 
no  water  is  entering  it  from  the  streams.  This  proves  that 
seepage  from  the  hillsides  add  to  the  volume  in  the  reservoir 
faster  than  water  was  lost  by  absorption. 


CHAPTER   IV. 
RUNOFF  AND   FLOW  OF  STREAMS. 

26.  Runoff. — By  "  runoff  "  is  meant  the  quantity  of  water 
which  flows  in  a  given  time  from  the  catchment  basin  of  a 
stream.     It  includes  not  only  that  portion  of  the  rainfall  which 
flows  over  the  surface  during  storms,  but  also  water  which  is 
derived  from  subsurface  sources,  as  springs,   etc.     The   runoff 
of  a  given  catchment  area  may  be   expressed   either   as  the 
number  of  second-feet  of  water  flowing  in  the  stream  draining 
that   area,  or  it  may  be   expressed  as  the  number  of  inches  in 
depth  of  a  sheet  of  water  spread  over  the  entire  catchment. 
The  latter  expression  indicates  directly  a  percentage  of  rainfall 
in  inches  which  runs  off.     Finally,  runoff  may  be  expressed 
volumetrically  as  so  many  cubic  feet  or  acre-feet. 

27.  Variability  of  Runoff.— As  runoff  bears  a  direct  rela- 
tion  to  precipitation,  it   appears   that,  knowing   the  amount 
of  rainfall  and  the  area  of  the  catchment  basin,  the  amount 
of  runoff  can  be  directly  ascertained.     This  is  not  the  caser 
however,   as    the    amount    of    runoff   is   affected    by   many 
varying  climatic   ard   topographic    factors.      Many   formulas, 
none  of  which  give  satisfactory  results,  have  been  worked  out 
for  obtaining  the  relation  between  runoff  and  precipitation.     If 
the  climate  be  the  same  over  two  given  catchment  basins,  the 
runoff  will  be  affected  by  the  depth  of  the  soil,  the  amount  of 
vegetation,  the  steepness  of  the  slopes,  and  the  geologic  struc- 
ture. 

The  climatic  influences  bearing  most  directly  on  runoff  are 
the  total  amount  of  precipitation,  its  rate  of  fall,  and  the  tem- 
perature of  air  and  earth.  Thus,  where  most  of  the  precipita- 

22 


FORMULAS  FOR   RUNOFF.  2$ 

tion  occurs  in  a  few  violent  showers  the  percentage  of  runoff 
is  higher  than  where  it  is  given  abundant  time  to  enter  the 
soil.  If  the  temperature  is  high  and  the  wind  strong,  much 
greater  loss  will  occur  from  evaporation  than  if  the  ground  is 
frozen  and  there  is  no  air  movement.  Within  a  given  drainage 
basin  the  rates  of  runoff  vary  on  its  different  portions.  Thus  in 
a  large  basin  the  rate  of  runoff  for  the  entire  area  may  be  low  if 
the  greater  portion  of  the  basin  is  nearly  level,  but  at  the  head- 
waters of  the  streams  where  the  slopes  are  steep  and  perhaps 
rocky  the  rate  of  runoff  will  be  higher.  The  coefficient  of  run- 
off increases  with  the  rainfall.  Thus  in  humid  regions  where 
the  rainfall  is  greatest  the  rate  of  runoff  is  highest. 

28.  Formulas  for  Runoff.  —  Several  formulas  for  ascertain- 
ing the  percentage  of  runoff  or  the  quantity  of  discharge  from 
a  given  catchment  basin  have  been  obtained  both  empirically 
from  known  measurements  and  by  theoretic  processes.  Mr. 
J.  T.  Fanning  found  by  plotting  a  curve  derived  from  the  flood 
discharges  of  some  American  streams  that  the  resulting  equa- 
tion for  flood  flow  became 


D=  2oo(My,    .......     (i) 

in  which  M  is  the  area  of  watershed  in  square  miles,  and  D  the 
volume  of  discharge  of  the  whole  area  in  second-feet. 

In  India  Colonel  Ryves  derived  the  following  formula  for 
runoff, 

D  =  C  VM*>      .......    (2) 

and  Colonel  Dickens  the  formula 

.......     (3) 


No  such  formulas  can  be  strictly  applied  with  the  same  co- 
efficient to  areas  of  varying  size,  and  all  must  be  used  with 
discretion,  as  their  results  are  greatly  influenced  by  different 
conditions  from  those  under  which  they  were  obtained.  In 
regions  where  maximum  recorded  rainfalls  of  from  3  to  6  inches 
in  24  hours  have  occurred  the  following  coefficients  have  been 
determined  : 


24  RUNOFF  AND  FLOW  OF  STREAMS. 

Rainfall  3.5  to  4  inches  in  flat  country,  C  —  200;  mixed 
country,  C  =  250  ;  hilly  country,  C  =  300 ;  and  for  a  maximum 
rainfall  of  6  inches,  C  varies  between  300  and  350.  For  Ryves' 
formula  the  coefficient  varies  between  400  and  500  in  flat  coun- 
try, and  for  hilly  areas  where  the  maximum  rainfall  is  high  it 
may  reach  650.  The  shape  of  the  catchment  basin  is  an  im- 
portant factor  in  the  formula  of  maximum  discharge. 

29.  Examples  of  Runoff. — On  the  headwaters  of  the  Ar- 
kansas River  in  Colorado,  at  altitudes  varying  between  7000 
and  14,000  feet,  the  depth  of  runoff  varies  between  20  and  50 
inches.  On  the  Arkansas  basin  above  Canyon  City  the  runoff 
averages  18  inches.  In  the  Sierras  in  Western  Nevada,  on  the 
headwaters  of  the  Truckee  and  Carson  rivers,  the  runoff  ranges 
between  25  and  45  inches  in  depth,  while  the  average  runoff 
over  larger  catchment  areas  on  these  streams,  above  Reno  and 
Genoa,  varies  between  14  and  25  inches.  In  nearly  every  case 
the  depth  of  runoff  is  about  60  per  cent  of  the  precipitation. 
In  Arizona  the  slopes  are  more  abrupt  and  barren  ;  yet,  as  the 
rainfall  is  less  regular  and  very  much  less  in  amount,  the  volumes 
of  runoff  are  much  smaller.  On  the  upper  Gila  River  basin  the 
total  depth  of  runoff  in  1890  for  15,000 square  miles  of  catchment 
basin  was  0.45  of  an  inch,  the  discharge  amounting  to  0.35 
second-feet  per  square  mile  of  catchment  area.  On  the  upper 
Salt  River  basin  above  Phoenix  the  depth  of  runoff  in  1890  was 
4.2  inches  and  the  discharge  of  the  stream  3.7  second-feet  per 
square  mile  of  catchment  area.  In  Montana,  on  the  head- 
waters of  the  Gallatin  and  Madison  rivers,  the  total  annual 
depth  of  runoff  averages  from  10  to  14  inches,  the  discharge 
varying  between  10  and  14  second-feet  per  square  mile  of 
catchment  area.  In  the  winter  it  is  as  low  as  0.4  second-foot, 
and  in  May  and  June  as  high  as  3  second-feet.  On  the  Rio 
Grande  basin  above  Del  Norte,  Colorado,  the  in  1890  was  annual 
runoff  amounts  to  about  10  inches  in  depth  or  to  10.5  second- 
feet,  while  on  the  entire  basin  of  the  Rio  Grande  above  El  Paso 
the  runoff  amounts  to  but  0.5  second-feet  per  square  mile  of 
catchment  area.  On  the  Bear  River  at  Collision,  Utah,  the 
annual  depth  of  runoff  is  about  6.6  inches,  and  the  discharge  6 


DISCHARGE    OF    WESTERN  RIVERS.  2$ 

second-feet  per  square  mile.  On  the  Provo  River  above  Provo, 
Utah,  the  runoff  amounts  to  10.5  second-feet  of  discharge  per 
square  mile.  On  the  Snake  River  above  Eagle  Rock,  Idaho, 
the  average  annual  runoff  is  14  inches  in  depth  or  10  second- 
feet  per  square  mile  of  catchment  area. 

30.  Flood  Discharges   of  Streams. — It   is   desirable  to 
know  the   monthly  and  daily  rates  of  runoff   as  well  as   the 
mean  annual  runoff  of  a  catchment  basin.     This  is  necessary 
in   order  that  dams  and  weirs  may  be  provided  with  ample 
wasteways.     The  greatest  floods  occur  either  on  barren  catch- 
ment basins  having  steep  slopes  or  where  heavy  snowfalls  are 
followed  by  warm,  melting  rains.     On  the  Gila  and  Salt  river 
basins  in  Arizona  the  percentages  of  runoff  are  exceptionally 
high  during  occasional  severe  storms.     The  highest  recorded 
flood  on  the  Salt  River  above  Phoenix  occurred  in  February, 
1891,  and  amounted  to  about  350,000  second-feet  from  a  catch- 
ment basin  of  12,260  square  miles.     This  is  equivalent  to  nearly 
30  second-feet   per  square  mile   of  catchment  area,  while  the 
stream  a  few  days  prior  to  the  occurrence  of  the  storm  was  not 
discharging  over  looo  second-feet,  or  one-twelfth  of  a  second- 
foot  per  square  mile. 

31.  Discharge  in  Seasons  of  Minimum  Rainfall. — Where 
the  number  of  storage  basins  is  limited  it  becomes  desirable  to 
save  all  of  the  water  possible  and  frequently  to  impound  enough 
to  carry  over  a  period  of  two  or  three  years  of  minimum  rain- 
fall.    In  general  it  has  been  found   that  cycles  of  mean  low 
rainfall  occur  every  two  or  three  years  when  the  amount   of 
precipitation  is  less  than  0.8  of  the  mean.     The  least  of  these 
three-year  low  cycles  has  been  found  to  average  as  low  as  0.7 
of  the  mean  annual  rainfall. 

32.  Regimen    of  Western    Rivers. — The  Eastern  rivers 
usually  drain  comparatively  level  catchment  basins,  well  cov- 
ered with  timber   and  giass.     As  a  result  of  this  the  soil  is 
deep  and  the  rate  of  runoff  is  consequently  low  and  the  streams 
are  comparatively  constant  in  their  discharge,  being  subject  to 
few  and  not  excessive  flood  rises.     This  is  because  the  larger 
portion  of  the  water  reaches  these  streams  from  subterranean 


26 


RUNOFF  AND   FLOW   OF  STREAMS. 


sources  by  seepage.     In  the  more  arid  portions  of  the  West 
the  regimen  of  the  streams  is  the  reverse  of  this.     The  catch- 


West  Gal  latin  • 

Madison 

Missouri 

Sun 

Yellowstone 

Cache  la  Poudre 

Arkansas 

Del-  Norte 

Embudo 

El  Paso 

Gila 

Salt 

East  Carson 

West    " 

Battle  Creeklg3 

Collinston    J-» 

Ogden 

Weber 

American  Fork 

Provo 

Spanish  Pork 

Sevier 

Henry  Pork 

Palls 

Teton 

Snake 

Owyhee 

Malheur 

Weiser 


FIG.  3.— MAXIMUM,  MINIMUM,  AND  MEAN  DISCHARGE  OF  SOME  WESTERN  RIVERS. 

ment  basins  are  precipitous  and  barren.     Little  water  soaks 
into  the  soil  to   supply  the   streams   from   springs.     After  a 


FLO W  AVAILABLE   FOR   STORAGE.  2/ 

heavy  storm  most  of  the  water  runs  off  in  a  very  short  period 
of  time,  resulting  in  great  floods.  Thus  streams  which  at  flood 
height  may  reach  from  10,000  to  15,000  second-feet  discharge 
for  a  few  hours  or  days  may  sink  within  a  week  or  so  to  paltry 
rills  of  a  few  second-feet  discharge  or  may  entirely  disappear. 
(Fig-  3-)  With  such  streams  it  becomes  necessary  to  so  design 
works  that  most  of  the  discharge  may  be  saved  by  storage 
within  a  short  period  of  time. 

33.  Mean  Discharge  of  Streams. — When  definite  data 
of  the  annual  discharge  of  a  stream  is  not  available  it  may  be 
obtained  approximately  by  multiplying  the  depth  of  runoff  in 
inches  into  the  area  in  square  miles  of  its  catchment  basin.   As 
shown  in  article  29,  the  proportion  of  rainfall  which  runs  off 
varies  between    50   and  80  per  cent,  according  as  the  slopes 
are  flat  or  steep,  wooded  or  barren.     The  discharge  ranges  be- 
tween 8  and  20  second-feet  per  square  mile  of  catchment  area. 

34.  Available  Annual  Flow  of  Streams. — Where  irriga- 
tion is  practised  all  of  the  water  flowing  in  the  streams  is  riot 
available  for  storage,  since  much  of  it  is  already  appropriated 
by  irrigators,  and  this  quantity  must  be  deducted  from  that 
available  for  storage.     A  large  portion  of  the  discharge  occurs 
in  winter  when  the  streams  are  covered  with  ice  which  renders  it 
practically  impossible  to  divert  the  water  for  storage,  though  it 
is  available  for  such  reservoirs  as  may  be  on  the  main  streams. 
As  nearly  all  of  the  flow  occurring  in  the  irrigating  season  is 
appropriated,  only  the  surplus  and  flood  water  is  available  for 
storage. 

35.  Works  of  Reference.     Evaporation,   Percolation, 
and  Runoff. 

BERESFORD,  J.   S.      Memorandum  on  the  Irrigation  Duty  of  Water. 

Prof.  Papers  on  Indian  Engineering,  No.  212.     Roorkee,  India. 
CRAIG,  JAMES.      Discharge  from  Catchment  Areas.     Trans.  Inst.  C.  E., 

vol.  80,  1884. 
FITZGERALD,  DESMOND.     Evaporation.     Trans.  Am.    Soc.  C.  E.,  vol. 

15,  1886. 
GREAVES,  CHARLES.     Evaporation  and  Percolation.    Trans.  Inst.  C.  E., 

vol.  45,  1875. 
NEWELL,  F.  H.     Hydrography.     Part  II,  nth,   I2th,  and   I3th  Annual 

Reports,  U.  S.  Geol.  Survey.     Washington,  D.  C.,  1890,  1891,  1892. 


CHAPTER  V. 
SUBSURFACE  WATER   SOURCES. 

36.  Sources  of  Earth  Waters. — The  water  which  enters 
the  soil  by  percolation  either  from  rain  or  from  canals,  reser- 
voirs, or  lakes  finds  its  way  through   the  soil  to  some  lower 
level  where  favorable  geologic   structure   enables  it  to  again 
reach  the  surface.    This  seepage  water  may  move  slowly  through 
the  particles  of  subsoil,  its  motion  being  rather  that  due  to 
absorption  or  capillary  attraction  than  to  direct  percolation  ; 
or  it  may  enter  some  seam  between  two  formations  from  which 
it  may  find  an  exit  perhaps  at  some  great  distance  through  a 
spring  or   artesian  well.     The  flow  of  water  by  percolation  is 
limited  not  only  by  the  degree  of  porosity  of  the  strata,  but  by 
their   inclination.     Yet    comparatively  impervious   rocks    fre- 
quently furnish  abundant  supplies  which  are  the  result  of  capil- 
lary attraction. 

37.  Sources  of  Springs  and  Artesian  Wells. — Wells  and 
springs  usually  derive  their  water  supplies  from  shallow  forma- 
tions as  gravels,  sands,  and  marls.     Their  temperature  may  be 
variable  owing  to  the  changes  in  the  temperature  of  the  surface 
of  the  soil,  while  their  flow  is  effected  by  precipitation  of  recent 
occurrence  and  by  evaporation  from  the  surface  of  the  ground. 

Gravitation  tends  to  draw  the  water  toward  the  centre  of 
the  earth,  and  it  percolates  in  that  direction  until  intercepted 
by  some  impervious  stratum  along  which  it  finds  its  way.  If 
the  water  fills  a  pervious  stratum  so  surrounded  by  impervious 
strata  that  it  is  prevented  from  escaping,  and  the  hydrostatic 
pressure  due  to  the  inclination  of  the  beds  is  sufficient  to  bring 
the  water  to  the  surface,  the  conditions  are  favorable  for  the 

28 


ARTESIAN    WELLS.  29 

production  of  an  artesian  well.  All  that  is  necessary  is  to 
pierce  the  upper  confining  stratum  by  boring,  when  the  water 
will  escape.  Generally  artesian  supplies  exist  in  the  newer 
sandstones  and  other  equally  porous  rocks.  Waters  are  fre- 
quently gathered  into  such  strata  from  distant  catchment 
basins.  Where  such  a  water-bearing  stratum  approaches  the 
surface  in  a  broad  plain  it  forms  an  extensive  artesian  basin. 

38.  Artesian  Wells. — Deep  wells  do  not  always  overflow. 
The  condition  of  overflow  depends  on  whether  the  pressure  is 
sufficiently  great  to  force  the  water  above  the  surface,  in  which 
case  they  are  known  as  artesian  wells.     Frequently  the  water 
will  reach  within  but  a  few  feet  of  the  surface,  when  an  ordi- 
nary well  or"  shaft  can  be  excavated  and  the  water  pumped  to 
the  desired  height.     In  many  other  cases  the  pressure  is  such 
that  the  water  spouts  forth  from  the  well  under  considerable 
pressure  to  great  heights.     In  an  artesian  area  of  considerable 
extent  the   various  wells  seriously   influence  each  other.     In 
the    San    Gabriel   and    San    Bernardino    valleys    in    Southern 
California  it  has  been  found  that   after  a  certain  number  of 
wells  have  been  sunk,  each  additional  well  affects  its  neighbors 
by  diminishing  their  discharge.     There  thus  comes  a  point  in 
the  sinking  of  wells  when  the  number  which  can  be  utilized  in 
any  given  area  or  basin  is  limited. 

39.  Examples    of  Artesian   Wells. — Some   great  wells 
have  been   sunk   in  different  parts  of  the  world.     The   cele- 
brated   Grinnell    well    in    Paris    has    an    8-inch    bore    and    is 
1806  feet  in  depth.     A  well  is  now  being  bored  in  the  neigh- 
borhood  of    Wheeling,   West  Virginia,  which   has  reached   a 
depth  of  over  5000  feet.     In  St.  Louis  is  a  well  which  reaches 
a  depth  of  3850  feet ;  about  3000  feet  below  the  sea-level.     In 
San  Bernardino  and  San  Gabriel  valleys  in  Southern  California 
and  in  the  upper  San  Joaquin  valley  in  the  neighborhood  of 
Bakersfield   are  some   very  extensive  artesian  areas,  but  the 
greatest  artesian  basins  of  the  West  are  found  in  the  neighbor- 
hood of  Waco,  Texas ;   Denver,  Colorado,  and  of  the  James 
river  valley  and  the  neighborhood  of  Huron  in  the  Dakotas. 

In  1890  there  were  8097  artesian  wells  on  farms  in  the  arid 
region.     Of  these  3210  were  in  California,  2524  in  Utah,  596  in 


3O  SUBSURFACE    WATER    SOURCES. 

Colorado,  and  between  460  and  530  each  in  North  Dakota, 
South  Dakota,  and  Texas,  besides  a  few  in  each  of  the  remain- 
ing States  and  Territories.  Of  these  wells  48^  per  cent  were 
used  in  irrigating  51,896  acres.  Their  average  depth  is  210 
feet ;  average  cost,  $245  ;  and  average  discharge,  54.4  gallons 
per  minute. 

40.  Supplying  Capacity  of  Wells. — The  supplying  capac- 
ity of  common  wells  is   frequently  increased  considerably  by 
irrigation.     As  water  is  applied  to  the  soil  through  a  period 
of  years  the  subsurface  level   rises   and  it  may  be  reached  at 
lesser  depths  than  previously.     In   this  way  irrigation  water 
may  be  used  over  several  times;  by  pumping  it  from  wells  it 
may  find  its  way  by  seepage  back  to  the  streams  from  which 
it  may  be  again  diverted. 

41.  Tunneling1  for  Water. — Tunnels  are  sometimes  driven 
in  sloping  or  sidehill  country  to  tap  the  subterranean  water 
supplies.     These  are  practically  horizontal  wells,  differing  from 
ordinary  wells  chiefly  in  that  the  water  has  not  to  be  pumped 
to  bring  it  to  the  level  of  the  surface,  but  finds  its  way  by 
gravity  flow  to  the  lands  on  which  it  is  to  be  utilized.     Near 
the  Kojah  Pass  in  India  is  a  great  tunnel  of  this  kind.     This 
is  run  near  the  dry  bed  of  a  stream  into  the  gravels  for  a  dis- 
tance of  over  a  mile.     The  slope  of  its  bed   is  3  in  1000,  its 
cross-section  is  1.7  X  3  feet,  and  its  discharge  about  9  second- 
feet.     The  Ontario  Colony  in  Southern  California  derive  their 
water  supply  from  a  tunnel  3300  feet  in  length,  run  under  the 
bed    of   San   Antonio    creek    through    gravel    and    rock.     Its 
cross-section  is  5  feet  6  inches  high,  3  feet  6  inches  wide  at 
bottom,  and  2  feet  wide  at  top.     It  is  partly  timbered  and 
partly  lined  with  concrete,  having  weep-holes  in  the  upper  part 
of  the  tunnel.     Its  discharge  is  about  6  second-feet.     The  sup- 
ply from  several  sub-tunnels  has  been  such  as  to  average  nearly 
10  second-feet  per  linear  mile  of  tunnel. 

42.  Other  Subsurface   Water   Sources. — Earth    waters 
may  be  gathered  for  irrigation  by  other  means   than  springs, 
common   or   artesian    wells,  or    tunnels.     In   portions   of   the 
plains   region,   especially  in  Kansas,  subsurface   supplies  have 


WORKS   OF  REFERENCE.  31. 

been  obtained  by  running  long  and  deep  canals  parallel  to  the 
dry  beds  of  streams  or  in  the  low  bottom  lands  and  valleys. 
These  canals,  acting  like  drainage  ditches,  receive  a  considerable 
supply  of  water  and  lead  it  off  to  the  lands.  In  the  dry  beds 
of  streams  in  California  submerged  dams  have  been  built  which 
reach  to  some  impervious  stratum  and  cut  off  the  subterranean 
flow,  thus  bringing  the  water  to  the  surface.  In  some  experi- 
ments made  on  two  subcanals  in  Kansas  the  amount  of  water 
obtained  was  15  second-feet  for  each  mile  in  length  of  excava- 
tion, which  was  6  feet  in  depth  below  the  subsurface  water.  It 
was  found  that  the  depth  and  length  were  the  controlling 
factors,  the  breadth  of  the  canal  having  little  effect  on  the 
amount  of  water  entering.  It  was  also  found  that  the  in- 
crease of  flow  due  to  the  deeper  cuts  was  nearly  as  the  square 
of  the  depth. 

43.  Works  of  Reference.    Artesian  Wells. 
CHAMBERLAIN,   T.  C.     The    Requisite  and  Qualifying   Conditions  of 
Artesian  Wells.     Fifth   Annual    Report,  U.  S.  Geological  Survey, 
Washington,  D.  C,  1884. 

GREGORY,  J.  W.,  and  COFFIN,  FRED.   F.  B.     Artesian  and  Underflow 
Investigation.     Department  of  Agriculture,  Washington,  D.  C.,  1892. 
HALL,  WM.  HAM.     Irrigation  in  Southern  California.     Part  II.    Sacra- 
mento, 1888. 

HAY,  Prof.  ROBERT,  and  Others.  Geological  Reports  on  Artesian 
Underflow  Investigation.  Department  of  Agriculture,  Washington 
D.  C.,  1892. 

HINTON,  RICHARD.  Artesian  and  Underflow  Investigation.  Depart- 
ment of  Agriculture,  Washington,  D.  C.,  1892. 

NETTLETON,  E.  S.     Artesian  and   Underflow   Investigation.     Depart- 
ment of  Agriculture,  Washington,  D.  C.,  1892. 
NEWELL,  F.  H.     Artesian  Wells  for  Irrigation.     U.  S.  Census  Bulletin 

No.  193.     Washington,  D.  C.,  1890. 

POWELL,].  W.  Artesian  Wells.  Part  II,  nth  Annual  Report,  U.  S. 
Geological  Survey.  Washington,  D.  C.,  1890. 


CHAPTER  VI. 
ALKALI,  DRAINAGE,  AND  SEDIMENTATION. 

44.  Harmful   Effects  of  Irrigation. — When  irrigation  is 
practised  without  proper  attention  to  drainage  it  is  liable  to 
result  in  the  following  evils:  (i)  production  of  alkali  or  floc- 
culent  salts  on    the    surface    of    the    ground ;    (2)    souring   or 
waterlogging  of  the  soil  due  to  supersaturation ;  (3)  fevers  and 
other  injurious  effects  the  result  of  the  same  cause. 

45.  Alkali.— The  white  efflorescent  salt  known  as  "alkali  "  is 
to  be  found  in  many  portions  of  the  West  both  as  a  result  of 
irrigation  and  occurring  naturally  over  extensive  areas.     These 
salts  have  been  analyzed  and  are  found  to  consist  chiefly  of 
chlorides,  carbonates,  and  sulphates  of  sodium.     Sometimes  a 
small  amount  of  potassium  salts,  sodium  phosphate,  or  man- 
ganese sulphate  are  present.     In  most  cases  sodium  sulphate 
predominates,  ranging  in  amount  from  5  to  75  per  cent.     The 
effect  of  this  alkali  on  the  surface  of  the  ground   is  to  kill  all 
vegetable  growth  and  to  render  the  soil  barren  and  unproduc- 
tive. 

46.  Causes  of  Alkali. — Where  the  natural  drainage  of  the 
country  is  defective  and  the   strata  underlying  the  surface  are 
impervious   or  the  soil  not  deep,   irrigation  or  rainfall  causes 
the  subsurface  water  plane  to  rise  to  such  a  height  that  finally 
the  soil  becomes  saturated.     Evaporation  then  takes  place  from 
the  surface,  and  as  this  process  continues  there  is  left  on  the 
soil  the  salts  contained    in  the  water.     Thus  the  more  water 
that  evaporates  from  the  surface  the  more  alkali  will  be  de- 
posited, and  increased  rainfall  or  irrigation  will  increase  the 
amount  of  alkali.     It  is  thus  seen  that  the  direct  cause  of  the 
production  of  alkali   is  the  rise  of  the  subsurface  water  plane 

32 


ALKALI  AND    WA  TER  LOGGING.  33 

due  to  defective  drainage.  Seepage  from  badly  constructed 
canals  is  a  great  producer  of  alkali.  Thus  where  the  velocity 
of  the  canal  is  slow,  time  is  given  for  water  to  soak  into  the 
soil  and  permeate  it. 

47.  Waterlogging.— Where  the  rise  of  water  from  the  sub. 
surface  or  its  addition  to  the  surface  from   natural  causes  or 
irrigation  is  more  rapid    than    the    losses   by    evaporation    or 
drainage,  the  water  stands  in   pools  and  the  soil  becomes  soft 
and  marshy,  producing  the  effect   known  as  "swamping"  or 
"  water-logging."    Like  alkali,  waterlogging  is  directly  traceable 
to  defective  drainage  and  the  careless  use  of  water.     Where  the 
conditions  are  sufficiently  well  balanced  for  drainage  to  prevent 
the  rise  of  the  subsurface  water  to  within  10  or  15  feet  of  the 
surface,  continued  irrigation  produces  good  results  by  soaking 
up  the  lower  strata  and  giving  an  abundance   of  water  near 
the    surface  for  wells  and  for  moistening  the    deeper  rooting 
plants. 

48.  Prevention  of    Alkali   and   Waterlogging. — Several 
preventatives  for  the  rise  of  alkali  or  the  excessive  soaking  of 
the  soil  have  been  recommended,  and  some  have  been  employed 
with  success.     Where  it   is  impossible  to   entirely  remove  the 
alkali,  the  cultivation  of  deep-rooting  or  such  plants  as  shade 
the  soil  and  reduce  the  amount  of  evaporation  may  permit  some 
use  to  be  made  of  the  land.     Irrigating  only  such  lands  as  have 
good  natural  drainage,  and  exercising  care  not  to  interfere  with 
this,  is  one  of  the  best  and  surest  preventives  of  the  production 
of    alkali    and    waterlogging.     The    introduction    of    artificial 
drainage  produces  the  same  effect,  while  in  a  lesser  degree  the 
same  result  may  be  obtained  by  the   use  of  deep   ditches  or 
furrows  which  themselves  act  as  drainage  channels.     When  the 
quantity  of  alkali  is    small  the  evil   effects  resulting  from  its 
presence  may  be  mitigated  by  the  application  of  chemical  anti- 
dotes, and    lastly   relief  may  be   obtained   in    some    cases  by 
watering  the  surface  and  drawing  off  the  water  without  allow- 
ing it  to  soak  into  the  ground.     This  system  of  reclaiming  the 
land  by  surface  washing  and  drawing  off  the  salt-impregnated 
water  is  known  as  "  leaching." 


34  ALKALI,  DRAINAGE,  AND   SEDIMENTATION. 

One  of  the  most  effective  methods  for  the  prevention  of 
alkali  is  the  judicious  and  sparing  use  of  water  in  irrigation. 
If  the  least  amount  of  water  necessary  for  the  production  of 
crops  is  applied  to  the  soil,  the  soaking  of  this  with  water 
will  be  a  much  slower  process  and  may  not  result  in  oversatu- 
ration,  even  though  the  drainage  be  defective. 

49.  Chemical  Treatment  and  Leaching. — A  cheap  anti- 
dote for  most  alkaline  salts  is  lime,  while  neutral  calcareous  marl 
will  answer  in  some  cases.     When  the  alkali  consists  of  car- 
bonates and  borates  the  best  antidote  is  gypsum  or  landplaster 
sown  broadcast  over  the  surface.     Leaching  may  be  practised 
by  building  temporary    embankments    around    the    land    and 
flooding,  then    rapidly  drawing   or   pumping  off   the   salt-im- 
pregnated waters. 

50.  Drainage. — Generally   the    drainage    of  irrigated  land 
will  take  care  of  itself  if  the  natural  drainage  channels  are  not 
interfered  with  or  obstructed.     Where  the  surface  has  a  mod- 
erate though  sufficient  slope  to  allow  the  water  to  flow  off,  or 
the  soil  is  underlain  by  deep  beds  of  gravel  or  porous  rocks 
which  will  carry  off  the   percolation  water,  irrigation  may  be 
practised  for  all  time,  and  even   an  excessive  amount  of  water 
may  be  used  without   seriously  affecting  the  crops.     In  a  few 
cases  the  drainage  may  be  improved  by  digging  drainage  chan- 
nels or  ditches  or  laying   drainage  pipes    under  the    surface. 
Such  methods  as  these,  however,  are  usually  too  expensive. 

In  many  portions  of  the  West,  and  especially  in  the  San 
Joaquin  Valley  in  California,  old  sloughs  and  abandoned  natu- 
ral drainage  lines  have  been  utilized  as  irrigation  channels. 
The  effect  of  this  is  bad,  as  the  natural  drainage  lines  thus  be- 
come overloaded,  resulting  in*  waterlogging  the  soil.  In  this 
way  large  areas  in  Fresno  County  and  its  neighborhood  have 
been  rendered  uncultivatable,  whereas  with  a  proper  system  of 
irrigating  channels,  providing  the  natural  drainage  channels  had 
been  left  open,  no  evil  effects  would  necessarily  have  resulted. 

51.  Excessive  Use  of  Water. — This  is  one  of  the  greatest 
evils  at  present  noticeable  in  our  Western  irrigation  methods. 
Almost  invariably  too    much  water  is  employed  in  irrigating 


SILT  AND   SEDIMENTATION.  35 

crops.  The  result  is  the  waste  of  water  and  the  oversaturation 
of  the  soil.  As  the  value  of  water  rises  it  will  be  used  with 
less  extravagance.  Proper  care  in  the  location  and  construction 
of  the  canal  banks  will  aid  greatly  in  reducing  the  evil  effects 
of  irrigation.  If  the  location  is  bad,  the  natural  drainage  chan- 
nels may  be  interfered  with.  If  the  construction  is  bad,  the 
loss  by  seepage  from  the  canal  into  the  soil  becomes  great. 

52.  Silt. — Great  volumes  of  silt  are  transported  by  Western 
rivers  in  times  of  flood.     This  is  the  result  of  the  erosion  of 
the    alluvial    banks  of  the    streams.      The   heavier  sand   and 
gravel  is  soon  deposited  in  the  upper  reaches  of  the  river,  and 
only  the  finest  silt  reaches  the  canals.     As  the  velocity  in  these 
is  relatively  low,  much  of  this  sediment  is  deposited  near  the 
canal  head,  in  storage  reservoirs  or  in  other  slack  water,  thus 
choking  the  canal  or  diminishing  the  volume   of  the  reservoir. 

53.  Amount  of  Sediment. — The  quantity  of  this  sediment 
which  is  carried  in  suspension  during  floods  is  frequently  greater 
than  is  generally  appreciated.     From  investigations  made  by  the 
U.  S.  Geological  Survey  on  the  Rio  Grande  in  1889  it  was  found 
to  range  from  J  to  \  of  I  percent  of  the  volume  of  flow.    It  was 
estimated  that  in  about  150  years  the  amount  of  this  sediment 
would  seriously  impair  a  reservoir  60  feet  in   depth.     On  the 
American  River  at  Folsom,  California,  in  one  year  a  depth  of 
nearly  10  feet  of  wet  silt  was  deposited  in  a  reservoir  at  that 
point ;  much  of  this,  however,  was  heavy  matter,-  as  gravels  and 
boulders  carried  by  the  swift  current  of  the  stream. 

54.  Prevention   of   Sedimentation    in   Reservoirs    and 
Canals. — There  are  practically  but  two  methods  of  mitigating 
the  injury  due  to  sedimentation  in  reservoirs.     One  is  by  build- 
ing higher  up  on  the  stream  cheap  settling  reservoirs  which  may 
be  destroyed  in  the  course  of  a  number  of  years,  or  the  dams 
be  increased  in  height  as  they  silt  up.     The  other  method  is  by 
the  construction  of  under-  or  scouring-sluices  in  the  bottom  of 
the  dam.     These  have  not  as  yet  proved  effectual,  as  their  in- 
fluence is  felt  at  but  a  short  distance  back  from  the   opening. 
Experience  has  shown  that  they  do  not  remove  silt  which  has 
already  been  deposited,  but,  providing  their  area  is  large  com- 


36  ALKALI,  DRAINAGE,  AND    SEDIMENTATION. 

pared  with  the  flood  volume  of  the  stream,  they  may  effectively 
prevent  the  deposition  of  sediment  by  permitting  the  silt-laden 
waters  to  flow  through  the  reservoir  ;  the  latter  only  being  filled 
after  the  flood  has  subsided  and  the  waters  become  less  turbid. 

Canals  should  be  so  designed  that  the  angle  at  which  they 
are  diverted  from  the  main  stream  shall  be  such  as  to  cause  the 
least  back  eddy  in  front  of  the  headgates  and  the  least  deposit 
at  that  point.  Where  a  canal  is  taken  off  at  right  angles  to  the 
line  of  the  stream  and  scouring-sluices  are  placed  in  the  weir 
immediately  adjacent  to  the  headgates,  the  main  stream  may 
be  so  trained  as  to  have  a  straight  sweep  past  the  headgates 
and  thus  scour  out  any  deposits  occurring  at  that  point.  In 
designing  a  canal  the  endeavor  should  be  to  so  change  the 
grade  with  the  cross-section  that  a  constant  velocity  shall  be 
maintained  throughout  the  main  line  and  all  its  minor  branches. 
In  this  event  the  silt  will  be  maintained  in  suspension  and  will 
be  carried  through  the  minor  ditches  and  not  deposited  until 
it  reaches  the  fields.  It  thus  becomes  valuable,  as  it  acts  as  a 
fertilizer.  As  the  velocity  of  the  current  is  generally  diminished 
in  the  upper  portion  of  the  canal  in  its  passage  from  the  main 
stream,  the  deposit  of  silt  is  likely  to  occur  at  this  point.  It 
may  be  well  to  encourage  this  by  increasing  the  cross-section 
of  the  canal  and  reducing  its  grade  so  that  its  capacity  shall 
remain  the  same  but  its  velocity  be  diminished.  Then  the  de- 
posit of  silt  will  occur  all  at  once  in  the  first  half-mile  or  less  of 
the  canal,  and  it  may  be  either  dredged  out  or  perhaps  scoured 
out  by  an  escape. 

55.  Fertilizing  Effects  of  Sediment.— The  value  of  silt- 
bearing  water  as  a  fertilizer  is  well  known.  Where  it  is  possi- 
ble to  keep  the  silt  in  suspension  until  the  water  reaches  the 
fields,  such  waters  are  especially  valued  for  purposes  of  irriga- 
tion. In  the  valley  of  the  Moselle,  France,  on  land  absolutely 
barren  and  worthless  without  fertilization,  the  alluvial  matter 
deposited  by  irrigation  from  turbid  water  renders  the  soil 
capable  of  producing  two  crops  a  year.  In  the  valley  of  the 
Durance,  France,  the  turbid  waters  of  that  stream  bring  a 
price  for  irrigation  which  is  ten  and  twelve  times  greater  than 


WEEDS.  37 

that  paid  for  the  clear  cold  water  of  the  Sorgues  River.  It  has 
been  estimated  that  on  the  line  of  the  Galloway  Canal  in  Cali- 
fornia land  which  has  been  irrigated  with  the  muddy  river 
water  gives  18  per  cent  better  results  after  the  fifth  year  than 
the  same  land  which  has  been  irrigated  with  clear  artesian 
water. 

56.  Weeds. — When  from  any  cause  it  becomes  necessary 
to  give  a  canal  a  low  velocity,  the  growth  of  water  weeds  and 
the  deposition  of  silt  are  encouraged.  Water-plants  grow 
most  freely  where  the  current  has  a  slow  velocity  and  the 
depth  is  such  that  the  sunshine  reaches  the  bottom.  They 
thrive  in  shallow  reservoirs,  thus  diminishing  their  capacity. 
Brush,  willows,  weeds,  and  rushes  may  encroach  on  the  chan- 
nels of  canals  where  the  slopes  of  the  banks  are  low  and  so 
diminish  the  water-way  as  to  greatly  reduce  their  carrying 
-capacity.  Providing  a  high  velocity  cannot  be  given  the  only 
possible  way  of  remedying  this  is  to  draw  off  the  water  and 
destroy  the  plants. 


CHAPTER  VII. 
QUANTITY  OF  WATER  REQUIRED. 

57.  Duty  of  Water. — The  duty  of  water  may  be  defined 
as   the    ratio    between    a    given    quantity    of   water   and   the 
amount  of  land  which  it  will  irrigate.     In  order  to  determine 
what  amount  of  water  is  sufficient  to  supply  a  given  area  of 
land  it  is  first  necessary  to  at  least  approximately  determine 
its  duty  for   the    specific   case    under  consideration.     On  the 
duty  of  water  depends  the  financial  success  of  every  irrigation 
enterprise,  for  as  water  becomes  scarce  its  value  increases.     In 
order  to  estimate  the  cost  of  irrigation  in  projecting  works,  it 
is  essential  to  know  how  much  water  the  land  will  require.     In 
order  to  ascertain  the  dimensions  of  canals  and  reservoirs  for 
the  irrigation  of  given  areas  the  duty  of  water  must  be  known. 

58.  Units  of  Measure  for  Water  Duty  and  Flow. — Be- 
fore considering  the  numerical   expression  of  water  duty,  the 
standard  units  of  measurement  should  be  defined.     For  bodies 
of  standing  water,  as  in    reservoirs,  the    standard   unit  is  the 
"  cubic  foot."     In  the  consideration  of  large  volumes  of  water, 
however,  the  cubic  foot  is  too  small  a  unit  to  handle  conven- 
iently and  the  "  acre-foot"  is  the  unit  employed  by  irrigation 
engineers.     This  is  the  amount  of  water  which  will  cover  one 
acre  of  land  one  foot  in  depth,  that  is  43,560  cubic  feet.     In 
considering  running  streams,  as  rivers  or  canals,  the  expression 
of  volume  must  be  coupled  with  a  factor  representing  the  rate 
of  movement.     The  time  unit  usually  employed  by  irrigation 
engineers  is  the  second,  and  the  unit  of  measurement  of  flow- 
ing water  is  the  cubic  foot  per  second,  or  the  "  second-foot  "  as 
it  is  called  for  brevity.     Thus  the  number  of  second-feet  flow- 

38 


UNITS   OF  MEASURE   FOR    WATER  DUTY  AND  FLOW.     39 

ing  in  a  canal  are  the  number  of  cubic  feet  which  pass  a 
given  point  in  a  second  of  time.  A  unit  still  generally  em- 
ployed in  the  West  is  the  "  miner's  inch."  This  differs  greatly 
in  different  localities  and  is  generally  defined  by  State  statute. 
In  California  one  second-foot  of  water  is  equal  to  about  50 
miner's  inches,  while  in  Colorado  it  is  equivalent  to  about  38.4 
miner's  inches.  The  period  of  time  during  which  water  is 
applied  to  the  land  for  irrigation  from  the  time  of  the  first 
watering  until  after  the  last  watering  of  the  season  is  usually 
known  as  the  "  irrigating  period."  This  is  generally  divided 
into  several  "  service  periods,"  by  which  is  meant  the  time 
during  which  water  is  permitted  to  flow  on  the  land  for  any 
given  watering.  Thus  the  irrigation  period  in  the  majority  of 
the  Western  States  extends  from,  say,  April  I5th  to  August 
1 5th,  about  120  days.  The  service  period,  or  the  duration  of 
one  watering,  is  generally  from  12  to  24  hours,  according  to  the 
soil  and  crop.  The  number  of  waterings  making  up  the 
irrigation  period  vary  between  2  and  5,  according  to  the  soil, 
climate  and  crop. 

In  the  following  table  are  given  some  few  convertible  units 
of  measure. 

TABLE  VI. 

UNITS  OF  MEASURE. 

second-foot  =  45°  gallons  per  minute. 

cubic  foot  =  7-5  gallons. 

cubic  foot  weighs  62$  pounds  at  average  temperature. 

second-foot  =  2  acre-feet  in  24  hours  (approx.). 

,000,000  cubic  feet  =  23  acre-feet,  (approx.). 

loo  California  inches  =  4  acre  feet  in  24  hours. 

100  Colorado  inches  =  5*  acre-feet  in  24  hours. 

50  California  inches  i  second-foot. 

38.4  Colorado  inches  =  i  second-foot, 

i  Colorado  inch  =  17,000  gallons  in  24  hours  (approx.). 

1  second-foot  =  59*  acre-feet  in  30  days. 

2  acre-feet  =  i    second-foot  per  day  or  .03^  second-feet 

in  30  days. 

100  California  inches  =     3-97  acre-feet  per  24  hours, 

i  acre-foot  =     25.2  California  miner's  inches  in  24  hours. 


4O  QUANTITY   OF    WATER   REQUIRED. 

59.  Measurement  of  Water  Duty. — The  duty  of  water 
may  be  variously  expressed   by  the  number  of  acres  of  land 
which  a  second-foot  of  water  will  irrigate  ;  or  by  the  number 
of  acre-feet  of  water  required  to   irrigate  an   acre  of  land;  or 
in  terms  of  the  total  volume  of  \vater  used  during  the  season. 
It  may  also  be  expressed  in  terms  of  the  expenditure  of  water 
per  linear  mile   of  canal,  though  this  form  can  only  be  satis- 
factorily  employed  when   the   location    of  the  canal  line  has 
been  previously  determined.     In  considering  the  duty  of  water 
care  should  be  taken  to  show  whether  it  is  reckoned  on  the 
quantity  of  water  entering  the  head  of  the  canal  or  the  quan- 
tity applied  to  the  land,  since  the  losses  by  seepage,  evapora- 
tion, etc.,  in  the  passage  of  water  through  the  canal  are  con- 
siderable.    Thus,  if  in  a  long  line  of    canal  the  duty  is  esti- 
mated at   150  acres  per  second-foot  and  the  losses  by  seepage 
and  evaporation  are  33^  per  cent,  the  duty  would  be  reduced 
to  100  acres  at  the  point  of  application. 

60.  Duty  per  Second-foot. — The  duty  of  water  in  various 
portions  of  the  West  is  a  matter  of  extreme  doubt.     As  re- 
cently as  in  1883  it  was  estimated  in  Colorado  to  be  from   50 
to  55    acres    per   second-foot.     In    Montana  and    portions  of 
Colorado  the  farmers  still  state  the  duty  as   being  one  miner's 
inch  to  the  acre,  or  38.4  acres  per  second-foot.     Recent  experi- 
ments  show    that   the    duty   is    rapidly    rising,  for  as  land  is 
irrigated  through  a  series  of  years  it  becomes  more  saturated, 
and  as  the  subsurface  water  plane  rises  the  amount  of  water 
necessary  to  the  production  of  crops  is  diminished.    The  culti- 
vation of  the  soil  causes  it  to  require  less  water.     The  adoption 
of  more   careful  methods  in   designing  and   constructing  dis- 
tributaries and  care  and  experience  in  handling  water  increase 
its  duty.  The  State  Engineer  of  Colorado  now  accepts  100  acres 
per  second-foot  as  the  duty  for  that  State.      In  Utah  60  acres 
per  second-foot  is  accepted  as  the  present  duty.     In  Montana 
it  is  about  80  acres  per  second-foot. 

In  the  following  table  the  duty  of  water  is  given  for  a  few 
foreign  countries  and  for  various  portions  of  the  West,  These 
duties  cannot  be  taken  as  fixed.  They  are  apt  to  be  increased 


DEPTH   OF    WATER  REQUIRED    TO   SOAK  SOIL.  41 

with  experience,  and  in  the  same  State  or  even  in  the  same 
neighborhood  they  will  differ  according  as  the  crops,  soil,  alti- 
tude, and  the  skill  in  handling  the  water  vary. 

TABLE  VII. 

DUTY   OF   WATER. 


Northern  India 250-300 

Valencia,  Spain , 200-325 

Northern  Chili 190 

Italy 65-70 

Colorado 80-100 

Utah ; 60-80 

Montana So-ioo 

Wyoming 70 

Idaho , 60 

New  Mexico 60 

Southern  Arizona loo 

San  Joaquin  Valley,  Cal 100-150 

Southern  California,  surface  irrigation 150-300 

sub-irrigation 300-500 

The  reason  for  the  high  duty  given  for  such  an  arid  region 
as  Southern  California  is  because  the  water  there,  being  valu- 
able, is  handled  with  great  care.  Where  sub-irrigation  is  em- 
ployed the  duty  has  in  some  cases  reached  as  high  as  1000 
acres  per  second-foot.  In  Wyoming,  where  care  was  taken  on 
an  experimental  farm  in  handling  water,  its  duty  was  found  to 
be  as  high  as  94  acres  on  oats  and  230  acres  on  potatoes. 

61.  Depth  of  Water  required  to  Soak  Soil. — Experi- 
ments conducted  in  India  have  shown  that  a  good  heavy  rain 
amounting  to  about  5j  inches  soaks  into  the  earth  to  a  depth 
of  from  16  to  18  inches.  If  this  amount  of  water  were  applied 
three  times  in  the  season,  it  would  be  equivalent  to  a  total  depth 
of  16^  inches  to  the  crop.  Experiments  made  in  Colorado 
showed  that  good  crops  could  be  raised  by  the  application  of 
a  depth  of  1 8£  inches  of  water,  while  in  Wyoming  12  inches 
applied  to  potatoes  and  24^  inches  to  oats  proved  sufficient. 
In  Idaho  the  depth  of  water  necessary  is  now  assumed  to  be 
about  2  feet,  while  in  Montana  15  to  18  inches  is  believed  to 
be  sufficient. 


42  QUANTITY  OF    WATER  REQUIRED. 

62.  Duty  per  Acre-Foot. — An  average  depth  of  3  inches 
of  water  on  the  surface  is  sufficient  to  thoroughly  water  an 
average   soil.     In  sandy  soil   4   inches   is  required.     This    is 
equivalent  to  10,454  cubic  feet,  or  about  \  of  an  acre-foot  per 
acre.     The  average  crop  requires  about  four  waterings  in  the 
season.     This  at  the  above  rate  would  be  equivalent  to  42,500 
cubic  feet,  or  nearly  an  acre-foot  per  acre.     From  the  results 
shown  in  article  61  it  will  be  seen  that  from  \\  to  2  acre-feet 
in   depth  applied  to  the  land  is  sufficient  to  irrigate  it.     In 
estimating   the  duty  of  water  stored  in  a  reservoir  allowance 
must  be  made,  however,  for  the  loss  due  to  evaporation  and 
absorption  in  conducting  the  water  to  the  fields.     As  this  will 
rarely  average  below  25  per  cent  it  follows  that  where  a  duty 
of  one  acre-foot  per  acre  is  possible  i£  acre-feet  must  be  stored 
in  the  reservoir,  and  where  2  acre-feet  per  acre  is  the  duty  2|- 
acre-feet  must  be  stored. 

63.  Linear  and  Areal  Duty.— From  experiments  made  in 
India   it  was  found  that  from  six  to  eight  second-feet  of  water 
should  be  allowed  per  linear  mile  of  canal.     This  quantity,  of 
course,  depends  on  the  area  on  either  side  of  the  canal  which 
it  will  command.     On  the  Soane  Canal  in  India  a  more  con- 
venient unit  was  employed,  it  having  been  discovered  that  about 
three  fourths  of  a  second-foot  was  sufficient  for  a  square  mile 
of  gross  area.     As  the  net  area  irrigated,  however,  is  rarely 
more  than  two  thirds  of  the  gross  area  commanded,  perhaps 
about  one  half  a  second-foot  is  sufficient  to  irrigate  a  square 
mile  when  the  most  economic  use  is  made  of  the  water. 

64.  Percentage   of    Waste    Land. — In    every    irrigated 
area  it  has  been  discovered  that  but  a  small  percentage  of  the 
total  area  commanded  is  irrigated  in  any  one  season.    Some  of 
the  land  is  occupied  by  roads,  farm-houses,  or  villages.     Some 
is  occupied  by  pasture  lands  which  receive  sufficient  moisture 
by  seepage  from  adjoining  irrigated  fields  ;  and  some  by  barn- 
yards, while  occasionally  fields  are  allowed   to  lie  idle  for  a 
season.     In  this  way  it  has  been  discovered  in  India  that  gen- 
erally but  two-thirds  to  four-fifths  of  the  total  area  commanded 
has  been  irrigated,  though  in  some  localities  this  percentage  is 


WOKA'S   OF   REFERENCE.  43 

a  trifle  larger.  This  is  particularly  so  in  the  neighborhood  of 
the  Soane  Canals  in  India,  where  about  500  acres  out  of  every 
640  are  irrigated.  From  estimates  made  of  the'area  under  cul- 
tivation in  well-irrigated  portions  of  the  West  it  has  been  dis- 
covered that  if  water  is  provided  for  500  out  of  every  640  acres, 
it  will  be  sufficient  to  supply  all  the  demands  of  the  cultivators. 
Keeping  this  in  mind,  it  will  be  seen  that  the  actual  duty  of 
water  when  estimated  on  large  areas  is  at  least  20  per  cent 
greater  than  the  theoretic  duty  per  acre. 

65.  Works  of  Reference.    Alkali.    Sedimentation  and 
Duty  of  Water. 

BERESFORD,  J.  S.  Duty  of  Water  and  Memoranda  on  Irrigation.  Pro- 
fessional Papers,  Second  Series,  No.  212.  Roorkee,  India 

CARPENTER,  L.  G.  Third  Annual  Report  on  Meteorology  and  Engin- 
eering Construction,  State  Agricultural  College  of  Colorado,  1890. 
Fort  Collins,  Colorado. 

DEAKIN,  ALFRED.  Royal  Commissioner  on  Water  Supply.  First  Prog- 
ress Report,  Irrigation  in  Western  America.  Melbourne,  1885. 

FLYNN,  P.  J.  Irrigation  Canals  and  other  Irrigation  Works.  Denver, 
Col.,  1891. 

FOOTE,  A.  D.  Report  on  Irrigation  of  Desert  Lands  in  Idaho.  New 
York,  1887. 

HALL,  WILLIAM  HAM.  Report  of  the  State  Engineer  to  Legislature  of 
California.  Sacramento,  1880. 

HILGARD,  E.  W.  Alkali  Lands.  Report  of  University  of  California. 
Sacramento,  Cal.,  1886. 

NEWELL,  F.  H.  Various  Bulletins  of  the  nth  Census  on  Irrigation  in 
Arid  States.  Washington,  D.  C,  1892. 

WILSON,  H.  M.  Irrigation  in  India.  Part  II,  I2th  Annual  Report  of 
the  U.  S.  Geological  Survey.  Washington,  D.  C.,  1891. 

American  Irrigation  Engineering.  Part  II,  isth  Annual  Report  of  the 
U.S.  Geological  Survey.  Washington,  D.  C.,  1892. 


CHAPTER    VIII. 
PRESSURE    AND    MOTION  OF   WATER 

66.  Physical  and  Chemical  Properties  of  Water. — Water 
is  composed  of  an  infinite  number  of  minute  particles,  each  of 
which  has  weight  and  can  receive  and  transmit  this  in  the  form 
of  pressure  in  all  directions.     The  particles  composing  water 
move    upon    and    among    each    other   with   an   inappreciable 
amount  of  friction.     Water  is  composed  of  at  least  two  atomic 
substances,  oxygen  and  hydrogen,  combined  in  the  ratio  of  one 
of  oxygen  to  two  of  hydrogen,  the  whole  forming  a  molecule 
of  water.     These  molecules  are  so  fine  that  it  has  been  esti- 

/v*— <JU^»»—    /<  j  "j  _<tjB<   11- 

mated  that  there  are  from  500  to  5000.  in  a  linear  inch. 

67.  Weight   of  Water. — Water    reaches    its    maximum 
density  at  about  39.2°  Fahrenheit,  and  the  weight  of  a  cubic  foot 
of  distilled  water  at  this  temperature  1562.425  pounds;  and  of  a 
U.  S.  gallon  8.3799  pounds.     Below  and  above  this  tempera- 
ture the  weight  of  a  given  volume  of  water  jgcreases.     The 
weight  of  a  cubic  foot  of  ice  is  57.2  pounds.     At  32°  Fahrenheit 
a  cubic  foot  of  distilled  water  weighs  62.417  pounds,  and  its 
weight    increases    from  this  to  the  maximum    density  above 
given,  from  which  it  decreases  to  62.367  pounds  at  60°  Fahren- 
heit, and  continues  to  decrease  almost  uniformly  to  a  weight 
of  59.707  pounds  at  a  temperature  of  212°,  which  is  the  boil- 
ing point  of  water.     Ordinary  pond,  brook,  or  spring  water  is 
heavier  than  distilled  water  because  of  the  trifling  amounts  of 
salts  carried  in  solution  in  most  fresh  waters,  while  salt  water  or 

44 


PKESSUXE    OF    WATER.  45 

water  laden  with  sediment  is  still  heavier,  according  to  the 
amount  of  mineral  or  suspended  matter  in  a  given  volume. 

68.  Pressure  of  Water. — Each  molecule  of  water  is  inde- 
pendently subject  to  the  force  of  gravity,  and  therefore  has 
weight.     When  water  is  pressed  by  its  own  weight  or  that  of  any 
other  force,  this  pressure  is  transmitted  equally  in  all  directions. 
The  pressure  at  any  point  of  a  volume  of  water  is  in  propor- 
tion to  the  vertical  depth  of  that  point  below  the  surface,  and 
is  independent   of  the  breadth  of  the  volume   of   water.     If 
water  be  contained  in  a  vessel  of  any  form  in  which  an  orifice 
is  made  the  particles  of  water  at  that  point  are  relieved  of  the 
resistance  of  the  confining  surface,  and  at  once  slide  on  each 
other  and  flow  out  of  the  orifice  with  a  velocity  proportional  to 
its  depth  below  the  surface,  or  to  what  is  known  as  the  "  head." 
The  pressure  due  to  a  column  of  water  in  a  vertical  tube  is 
directly  proportional  to  its  height,  and  if  the  column  be  bent 
or  inclined  at  any  angle  the  pressure  will  not  be  dependent  on 
the  length  of  the  crooked  confining  channel,  but  to  the  height 
of  the  surface  vertically  below  the  lowest  part  of  the  column. 

69.  Amount  of  Pressure  of  Water.— A  cubic  foot  of  water 
is  ordinarily  taken  as  weighing  62.5  pounds,  and  the  pressure  per 
square  inch  for  each  vertical  foot  of  depth  below  the  surface 
of  water    is  about  0.434  pound.     By  means  of  the  ordinary 
methods  adopted  in  considering  the  parallelogram  of  forces, 
the  pressure  of  a  body  of  water  against  an  inclined  surface  at 
any  given  point  may  be  determined  by  representing  the  depth 
(or  the  weight  due  to  the  depth  at  that  point)  by  a  line,  the 
length  of  which  bears  a  certain  proportion  to  the  weight,  and 
by  resolving  this  inclined  line  into  its  resultant  horizontal  and 
vertical  components,  these  latter  will  then  represent  the  relative 
horizontal  and  vertical  pressures  exerted  by  the  water  against 
that  point.     To  find  the  total  pressure  of  water  on  any  surface 
its   area   in  square  feet  should  be  multiplied  by  the   vertical 
depth  of  its  centre  of  gravity  below  the  water  surface  in  feet, 
and  the  total  by  the  weight  of  one  cubic  foot  of  water. 

Making  //  =  to  the  head  or  depth  below  the  surface,/  — 
the  pressure  in  pounds  at  that  point,  and  g  the  depth  of  the 


4-6  PRESSURE   AND   MOTION  OF    WATER. 

centre  of  gravity  of  the  mass  of  water  below  the  surface,  or 
one  half  of  /i,  and  the  weight  of  a  cubic  foot  of  water  being 
62.5  pounds,  we  have/  =62.  ^hg. 

70.  Centre  of  Pressure.— The  force  which  tends  to  over- 
turn or  push  a  surface  about  a  given  point,  is  not  in  the  centre 
of  gravity  of  the  body  of  water,  but  at  two  thirds  of  the  depth 
from  the  surface  to  that  point,  and  is  known  as  the  centre  of 
hydrostatic  pressure,  while  the  centre  of  gravity  is  at  one  half 
the  vertical  depth  of  the  point.  The  total  pressure  upon  a 
curved  surface  is  proportional  to  the  total  length  of  that  sur- 
face, but  the  horizontal  effect  of  this  pressure  is  directly  pro- 
portional to  the  vertical  projection  of  the  surface. 

71.  Atmospheric  Pressure. — The  weight  of  the  atmosphere 
upon  the  surface  of  any  substance  at  the  level  of  the  sea  is 
about  14.75  pounds  per  square  inch.  This  quantity  is  known 
as  an  atmosphere,  and  will  sustain  a  column  of  water  34.028 
feet  in  height.  In  other  words,  the  pressure  of  the  atmos- 
phere would  raise  a  column  of  water  to  this  height.  It  is  on 
this  account  that  it  is  possible  to  raise  water  by  pumping  or 
to  cause  water  to  flow  through  a  siphon.  The  act  of  pump- 
ing or  of  raising  water  by  a  siphon  produces  a  vacuum  above 
the  water,  and  the  pressure  of  the  atmosphere  forces  the  water 
up  to  fill  this  vacuum  to  a  height,  approximately,  of  34  feet. 
Owing,  however,  to  friction  and  other  causes,  water  can  never 
be  raised  to  quite  this  height ;  while  at  altitudes  above  the  sea- 
level  where  the  atmosphere  is  lighter,  its  sustaining  power  is 
diminished  and  the  height  to  which  it  will  force  water  is  dimin- 
ished proportionately. 

72.  Motion  of  Water. — The  motion  of  water  is  due  to  a 
destruction  of  the  equilibrium  among  the  particles  forming  its 
mass,  and  it  is  said  to  "  flow  "  because  the  action  of  gravity 
generates  motion  and  destroys  equilibrium.  The  motion  of  a 
falling  body  is  constantly  accelerated  by  the  force  of  gravity  in 
regular  mathematical  proportion.  At  the  level  of  the  sea  a 
body  falling  freely^  vacua  drops  a  height  of  16.1  feet  during 
the  first  second  of  time,  its  velocity  at  the  end  of  the  first 
second  being  32.2  feet,  and  it  is  accelerated  by  this  amount 


MOTION   OF  WATER,  47 

for  each  succeeding  second.  It  is  this  quantity  which  is  known 
as  the  acceleration  of  gravity,  and  which  is  usually  designated 
by  the  letter  g  in  hydraulic  formulas.  The  velocity  g  of  a 
body  at  the  end  of  a  given  space  of  time  is  equal  to  the  pnxU 
uct  of  time  into  its  acceleration'  by  gravity.  Thus,  v  =  gt. 
It  has  been  shown  that  the  height  //,  through  which  the  body 
falls  or  through  which  its  pressure  is  accelerated,  is  equal  to  one 
half  of  the  gravity,  and  the  heights  fallen  in  any  given  time  are 

l~2.h 
as  the  squares  of  the  time ;  hence  /  —  \  /  — ,and  substituting, 

V  g 

transposing  and  eliminating  we  have  z/-=  V2gh. 


CHAPTER   IX. 

FLOW   AND   MEASUREMENT   OF   WATER   IN   OPEN 
CHANNELS. 

73.  Factors  affecting  Flow. — If  an  open  channel  be  given 
the  smallest  possible  inclination  in  one  direction,  the  water  con- 
tained therein  will  be  at  once  set  in  motion  by  the  act  of  grav- 
ity, and  its  particles  will  fall  one  over  the  other  in  the  direction 
of  the  inclination  until  motion  or  flow  in  that  direction  takes 
place.  The  effect  of  the  action  of  gravity  to  produce  motion  is 
dependent  on  the  slope,  and  this  is  usually  represented  by  the 
ratio  of  the  vertical  to  the  horizontal  distance ';  so  we  have  as 
factors  representing  the  velocity  of  flow  the  length  of  the 
channel,  /,  for  a  vertical  fall  of  any  given  height,  &  The 
amount  of  friction  offered  by  the  sides  of  the  channel  to  the 
flow  of  water  and  tending  to  impede  its  velocity  is  one  of  the 
important  factors,  and  is  dependent  chiefly  on  the  nature  of 
the  bed  and  sides  of  the  channel,  that  is,  to  the  lining  or  sur- 
face of  the  channel  against  which  the  water  flows,  and  on  the 
length  of  wetted  perimeter  or  the  sectional  area  against  which 
the  water  presses.  Other  quantities  on  which  the  coefficients 
of  flow  in  channels  depend  are  the  hydraulic  mean  depth,  r, 
which  is  equal  to  the  area  of  the  cross-section  of  the  water  in 
square  feet,  A,  divided  by  the  vv'etted  perimeter  in  linear  feet, 
/.  A  simple  formula  representing  the  mean  velocity  of  flow  is 


--\J~'     Vri, 

in  which  i  is  the  sine  of  the  inclination  h  divided  by  /in  feet ; 
h  being  the  fall  of  the  water  surface  in  the  distance  /;  m  is  a 

48 


FORMULAS   OF  FLOW  IN    OPK.\     CHANNELS.  49 

variable  coefficient,  which  includes  most  of  the  minor  modify- 
ing factors.  Tables  of  the  value  of  m  are  published  in  nearly 
all  books  on  hydraulics,  from  which  it  will  be  found  that  m 
varies  between  .05  for  a  hydraulic  mean  radius  of  .25,  to  .0298 
for  a  hydraulic  mean  radius  of  i,  and  diminishes  constantly 
thence  to  a  value  of  .0074  for  a  hydraulic  mean  radius  of  10, 
and  .002  to  a  hydraulic  mean  radius  of  25. 

74.  Formulas  of  Flow  in  Open  Channels. — There  are 
many  formulas  for  finding  the  mean  velocity  of  flow  in  open 
channels.  These  have  all  constant  coefficients,  and  are  there- 
fore incorrect  outside  of  a  small  range  of  dimensions.  Re- 
cently, as  a  result  of  experiments  on  the  Mississippi  by  Hum- 
phreys and  Abbot,  and  of  experiments  made  in  India,  Kutter 
has  devised  a  formula  which  takes  into  account  the  resistance 
due  to  the  varying  quantities  n  and  k,  which  depend  on  the 
nature  of  the  surface  of  the  channel.  Bazin  made  some  experi- 
ments on  small  canals,  from  which  he  devised  a  formula  which 
has  received  popular  favor.  This  formula  is  arranged  with 
various  constant  factors,  according  to  the  four  grades  of  rough- 
ness of  the  surface  of  the  channel.  Modifications  of  this 
formula  have  been  devised  by  D'Arcy  which  are  still  more  con- 
venient to  use.  D'Arcy 's  formula  is 


/  10002 

v  —  r\-  — 

V    .o8«Ur4-o.3< 


in  which  i  equals  the  fall  of  water  in  any  distance,  /  divided  by 
that  distance  =  —  =  the  sig**  of  the  slope. 

75.  Kutter's  Formula.—  The  formula  which  is  now  most 
approved  for  determining  the  velocities  of  flow  in  open  chan- 
nels is  Kutter's  formula, 


.8n  .00281 

f  41.6  + 


X  Vri. 


SO  FLO W  AND  MEASUREMENT  OF    WATER. 

Substituting  for  the  first  term  of  the  right-hand  factor  the  letter 
C,  we  have  Chezy's  formula 

v=  CVrl 

For  small  channels  of  less  than  20  feet  bed  width  Bazin's 
formula  gives  fair  results  where  the  sides  and  bottom  are  well 
built.  The  coefficients  in  this  formula  depend  on  the  nature 
of  the  surface  of  the  material  and  the  hydraulic  mean  depth. 
The  following  table,  from  Flynn's  "  Flow  of  Water  in  Open 
Channels,"  gives  the  value  of  C  for  a  wide  range  of  earth-chan- 
nels, and  will  cover  nearly  everything  occurring  in  ordinary 
practice. 


TABLE  VIII. 

VALUE  OF  C  FOR  EARTH  CHANNELS  BY  KUTTER'S  FORMULA. 


«  =  .022 

»  -  -°J5 

1 

'  r  in  fee 

t. 

1 

'/•in  fee 

t. 

I  iii. 

0.4 

I.O 

1.8 

2.5 

4.0 

0.4 

I.O 

1.8 

2-5 

4.0 

C 

C 

c 

c 

C 

C 

c 

C 

c 

C 

IOOO 

35-7 

62.5 

80.3 

89.2 

99-9 

19.7 

37-6 

51.6 

59-3 

69.2 

1250 

35-5 

62.3 

80.3 

89.3 

100.2 

19.6 

37-6 

51.6 

59-4 

69.4 

1667 

35-2 

62.1 

80.3 

89.5 

100.6 

19.4 

37.4 

51-6 

59-5 

69.8 

2500 

34-6 

61.7 

80.3 

89.8 

101.4 

I9.I 

37-1 

51-6 

59-7 

70.4 

3333 

34. 

61.2 

80.2 

90.1 

TO2.2 

18.  8 

369 

51.6 

59-9 

71.0 

5000 

33- 

60.5 

80.3 

90.7 

'03-7 

18.3 

364 

51.6 

60.4 

72.2 

7500 

31.6 

59-4 

80.3 

91-5 

106.0 

17.6 

35-8 

51-6 

60.9 

73-9 

IOOOO 

30-5 

53-5 

80.3 

92.3 

107.9 

17-1 

35-3 

51.6 

60.5 

75-4 

15840 

28.5 

56.7 

80.2 

93-9 

112.  2 

16.2 

34-3 

51.6 

62.5 

78.6 

20000 

27.4 

55-7 

80.2 

94.8 

II5-0 

15.6 

33-8 

51-5 

63.1 

80.6 

•  a-V 

This  table  is  arranged  with  two  different  values  for  the 
factor  n  which  are  dependent  on  different  qualities  of  surface 
in  the  channel.  The  accuracy  of  Kutter's  formula  depends 
chiefly  on  the  selection  of  the  coefficient  of  roughness  n,  and 
experience  is  required  in  order  to  give  the  right  value  to  this 
coefficient/  In  order  to  provide  for  the  future  deterioration  of 
the  channel  surface  by  the  growth  of  weeds  or  its  abrasion,  it 


DISCHARGE    OF   STREAMS  AND    VELOCITIES   OF  FLO IV-    5  I 

is  well  to  select  a  high  value  for  n.     The  following  are  some  of 

the  values  of  n  for  different  materials  as  derived  from  Jackson, 

Hering,  Kutter,  and  others : 

n  =  .009  for  well-planed  timber ; 

n  =  .01   for  plaster  in  cement,  glazed  iron  pipes,  and  glazed 

stoneware  pipes; 
n  —  .012  for  rough  timber ; 

n  —  .013  to  .017  for  ashlar  masonry,  tuberculated  iron  pipes, 
and  brickwork  according  to  the  smoothness  of  the  sur- 
face and  its  condition  ; 

n  —  .02  for  rubble  in  cement  and  coarse  rubble  of  nearly  all 
kinds ;  also  for  coarse  gravel  carefully  laid  and  rammed, 
or  for  rough  rubble  where  the  interstices  have  become 
filled  with  silt ; 

n  •=  .0225  in  good  earth  canals ; 

n  =  .025  to  .03  in  canals  from  those  having  tolerably  uniform 
cross-section  and  slopes  to  those  which  are  in  rather  bad 
order,  and  have  some  stones  and  weeds  obstructing  the 
channels ; 

n  =  .035  to  .05  from  canals  and  rivers  with  earth  beds  in  bad 
order  and  obstructed  by  stones,  etc.,  to  torrents  covered 
with  all  varieties  of  detritus. 

76.  Discharge  of  Streams  and  Velocities  of  Flow.— 
The  quantity  of  discharge  of  a  canal  or  river,  Q,  in  second- 
feet  is  obtained  by  multiplying  its  velocity,  v,  in  feet  per 
second  into  the  cross-sectional  area,  A,  of  the  channel  in 
square  feet.  Algebraically  expressed,  Q  =  Av. 

Since  the  discharge  of  an  open  channel  depends  primarily  on 
a  knowledge  of  its  mean  velocity,  it  will  be  well  to  consider  the 
relation  of  this  to  the  velocities  in  other  portions  of  the  chan- 
nel. In  any  open  channel  the  film  of  water  in  contact  with 
the  open  air  has  a  velocity  which  is  a  trifle  slower  than  that  in 
the  centre  of  the  mass  owing  to  the  retarding  effect  of  friction 
against  the  atmosphere.  This  velocity  is  known  as  the  surface 
velocity.  The  velocities  of  the  films  adjacent  to  the  sides  and 
bottom  of  the  channel  are  retarded  to  a  still  greater  extent  by 
the  roughness  of  the  same,  and  in  direct  proportion  to  this 


52  FLOW  AND   MEASUREMENT  OF    WATER. 

roughness.  It  has  been  found  that  in  a  channel  of  trapezoidal 
cross-section,  with  an  average  depth  to  width,  the  film  of  water 
%  having  a  mean  velocity  of  the  entire  channel  is  located  in  the 
centre  of  the  channel  and  at  a  point  about  one-third  of  the 
depth  below  the  surface. 

77.  Surface  and  Mean  Velocities. — The  surface  velocity 
is  that  which  is  most  readily  obtainable  by  simple  methods. 
Experiments  have  been  made  by  DuBuat,  Francis,  Brunningr 
and  others  to  determine  the  ratio  of  the  maximum  to  the  sur- 
face velocity.     From  these  it  has  been  found  that  the  approxi- 
mate mean  velocity  v  —  .91 5  V,  in  which  large    Fis  the  central 
surface  velocity.     In    other  experiments  the    ratio    has   been 
found  to  vary  between  .911   and   .915.     From  careful  experi- 
ments made  in  Germany  it  has  been  found  that  the  mean  veloc- 
ity bears  the  ratio  to  the  mean  surface  velocity,  account  being 
taken  for  the  reduction  toward   the  shore,  of   about   .837.     It 
will  thus  be  seen  that  the  ratio   of  the   surface   to   the   mean 
velocity  varies  with  the  section  of  the  channel,  and  with   the 
roughness  of  its  sides  as  well  as  with  the  depth. 

78.  Measuring   or    Gauging   Stream    Velocities. — One 
of  the  simplest  methods  of  gauging  the  velocity  of  a  stream/ 
but  one  which  does  not  give  the  most  accurate  results,  is  by 
means  of  simple  wooden  floats  or  bottles,  or  some  similar  con- 
trivance, thrown  into  the  centre  of  the  stream  and  timed  for  a 
given  distance.     For  convenience  100  feet  maybe  measured  off 
on  the  bank  and  the  time  of  the   float  ascertained  in  passing 
over  this  distance.     This  will  give  the  central   or  maximum 
surface  velocity.     The  mean  surface  velocity  may  be  obtained 
by  throwing  a  number  of    floats  in  different   portions  of  the 
surface  of  the  stream.     This  quantity  multiplied  by  .Swill  give 
approximately  the  mean  velocity  of  the  stream. 

The  velocity  of  the  stream  may  be  ascertained  with  still 
more  accuracy  by  getting  the  mean  velocity  not  of  the  surface 
but  of  the  entire  body  of  the  stream  by  means  of  upright 
wooden  floats  so  weighted  that  their  bottoms  shall  float  within 
a  few  inches  of  the  bed  of  the  channel.  A  number  of  these 
placed  in  different  portions  of  the  cross-section  of  the  stream 


CURREN7'  METERS. 


53 


and  timed  over  a  course  of  a  given  length  should  give  the 
mean  velocity  of  the  channel.  In  making  careful  gaugings  of 
this  sort  the  stream  should  be  divided  accurately  into  sections, 
and  each  float  be  permitted  to  pass  down  its  section. 

79.  Current  Meters. — Current  meters  are  mechanical  con- 
trivances so  arranged  that  by  lowering  them  into  the  stream 


FIG.  4.— COLORADO  CURRENT  METER. 


the  velocity  of  the  current  can  be  ascertained.  Various  forms 
of  current  meters  have  been  designed  and  used,  the  two  gen- 
eral classes  being  the  direct-recording  meter,  in  which  the 


54  FLOW  AND   MEASUREMENT   OF    WATER. 

number  of  revolutions  is  indicated  on  a  series  of  small  gear- 
wheels driven  directly  by  a  cog-and-vane  wheel.  And  the 
electric  meter,  in  which  the  counting  is  done  by  a  simple  make- 
and-break  circuit,  the  registering  contrivance  being  placed 
any  desired  distance  from  the  meter.  There  are  several  differ- 
ent makes  of  current  meters  of  both  kinds.  Of  direct-acting 
meters,  that  which  has  recently  found  favor  in  the  West  is 
known  as  the  Colorado  meter,  and  is  employed  by  the  hydro- 
graphers  of  the  U.  S.  Geological  Survey,  Fig.  4.  The  stem 
a  is  of  iron  pipe,  several  lengths  of  which  maybe  joined  to- 
gether, though  it  is  difficult  to  handle  if  over  8  feet  in  length. 

There  are  several  varieties  of  electric  meters,  one  of  which, 
Price's,  has  been  received  with  considerable  favor.  This  meter, 
however,  like  most  of  those  which  are  employed  in  the  Eastern 
States  is  not  satisfactory  in  Western  practice,  since  the  Western 


FIG.  5. — HASKELL  CURRENT  METER. 

streams  are  so  charged  with  sediment,  weeds  and  driftwood 
in  times  of  flood  that  the  ordinary  meter  becomes  clogged. 
The  meter  which  has  found  the  most  favor  in  the  West. and  is 
used  by  the  hydrographers  of  the  U.  S.  Geological  Survey  is  a 
modification  of  the  Haskell  meter,  Fig.  5. 

80.  Gauging  Stations. — The  first  operation  in  making  a 
careful  gauging  of  velocity  by  means  of  a  current  meter  is  the 
choosing  of  a  good  station.  This  consists  in  finding  some  point 
on  the  course  of  the  stream  where  its  bed  and  banks  are  nearly 
permanent,  the  current  of  moderate  velocity,  and  the  cross- 
sections  are  uniform  for  about  100  feet  above  and  below  the 
gauging  station.  At  this  point  a  wire  should  be  stretched 


USE    OF    THE    CURRENT  METER.  55 

across  the  stream  and  tagged  with  marks  placed  every  5,  10,  or 
20  feet  apart,  according  to  the  width  of  the  stream.  An  inclined 
gauge  rod  is  firmly  set  into  the  stream  at  some  point  where  it 
can  be  easily  reached  for  reading,  and  gauge  heights  are  re- 
corded through  a  long  period  of  time  in  order  that  variations 
in  the  velocity  and  discharge  may  be  had  for  different  flood 
heights. 

81.  Use  of  the  Current  Meter. — The  current  meter  may 
be  conveniently  used  either  from  a  boat  attached  to  a  wire 
cable  strung  a  little  above  the  tagged  wire,  or  from  a  bridge 
which  does  not  impede  the  channel  so  as  to  make  currents  or 
eddies  in    the  water.     In   using   the  direct-acting   meter    the 
gauger  holds  it  in  his  hands  by  the  rod,  and  inserting  it  in  the 
water  at  any  desired  depth  allows  it  to  register  for  a  certain 
number  of  seconds.     In  obtaining  the  mean   velocity  of  the 
stream  he  plunges  it  slowly  up  and  down  from  the  bottom  of 
the  stream  to    its    surface   a    few    times    for   a   given    length 
of  time  at  each  section  marked  on  the  tagged  wire,  and  in  this 
way  gets  the  mean  velocity  of  each  section.     The  area  of  this 
section  is  of  course  already  ascertained  by  a  cross-section  made 
by   measurement   or    sounding  of  the  stream,  and  the    mean 
velocity  multiplied  into  the  area  of  each  section  gives  the  dis- 
charge at  that  point.     Care  must  be  taken  to  hold   the   rod 
vertically,  as  any  inclination  of  the  meter  materially  affects  its 
record. 

In  using  the  Haskell  meter  it  is  suspended  and  inserted  in 
the  same  manner  for  moderately  shallow  streams,  but  in  deep 
flood  streams  it  is  generally  suspended  by  a  wire  instead  of 
being  pushed  down  by  a  rod,  and  a  very  heavy  weight  is  attached 
to  its  bottom  to  cause  it  to  sink  vertically.  In  the  Colorado 
meter  the  registering  wheels  are  stopped  and  started  by  pulling 
a  wire  which  throws  the  wheels  in  and  out  of  gear.  With  the 
Haskell  meter  the  registering  is  done  by  electricity, 

82.  Rating  the  Meter. — Before  the  results  can  be  obtained 
each  meter  must  be   rated  ;  that  is,  the  relation  between  the 
number  of  revolutions  of  the  wheel  and  the  velocity  of  water 
must   be   ascertained.     This   is  usually  done  by  drawing  the 


56  FLO W  AND   MEASUREMENT  OF    WATER. 

meter  through  quiet  water  over  a  course  the  length  of  which  is 
known,  and  noting  the  time.  From  the  observations  thus 
made  the  rating  is  determined  either  by  formula  or  by  graphic 
solution.  The  distance  through  which  the  meter  is  drawn 
divided  by  the  time  gives  the  rate  of  motion  or  velocity  of  the 
meter  through  the  water.  The  number  of  revolutions  of  the 
wheel  divided  by  the  time  gives  the  rate  of  motion  of  the 
wheel.  The  ratio  of  these  two  is  the  coefficient  by  which  the 
registrations  are  transformed  into  velocity  of  the  current.  This 
is  not  a  constant.  Taking  the  number  of  registrations  per 
second  as  abscissae  represented  by  x,  and  the  velocity  in  feet 
per  secon'd  as  ordinates  represented  by  j,  we  get  the  equation 
y  =  ax-\-b,  in  which  a  and  b  are  constants  for  the  given 
instrument. 

In  determining  the  rating  of  the  meter  graphically,  the 
values  of  x  and  y  gotten  directly  from  the  instrument  are 
plotted  as  co-ordinates,  using  the  revolutions  per  second  as 
abscissae  and  the  speed  per  second  as  ordinates.  In  this  way 
a  series  of  points  are  obtained  through  which  a  connecting 
line  is  drawn,  giving  the  average  value  of  the  observations. 
Prom  the  position  of  the  line  thus  plotted  the  coefficient  of 
velocity  can  be  read  off  corresponding  to  one,  two,  or  any 
number  of  revolutions  per  second.  When  in  actual  use  it  is 
evident  that  at  each  rate  of  speed  of  the  meter  there  is  a 
different  coefficient  of  velocity.  Three  or  four  of  these  for 
average  variations  in  velocities  may  be  used  in  getting  the 
true  velocity  from  the  meter  record. 

83.  Rating  the  Station.— After  daily  readings  of  the  gauge 
height  of  the  water  have  been  taken  at  the  station  for  some 
time,  and  the  velocity  measured  by  means  of  the  meter  at 
different  heights  of  stream,  the  results  should  be  plotted 
on  cross-section  paper,  with  the  gauge  heights  as  ordinates  and 
the  discharges  (obtained  by  multiplying  the  velocities  into  the 
cross-section)  as  abscissae.  These  points  generally  lie  in  such 
a  direction  that  a  line  drawn  through  them  gives  nearly  half  a 
parabolic  curve  and  represents  the  discharge  for  different 
heights.  Having  once  plotted  this  line  it  becomes  possible  to 


MEASURING    WEIRS, 


57 


determine  the  discharge  of  the  stream  at  any  time  by  knowing 
the  height  of  the  water  from  the  gauge-rod. 

84.  Measuring   Weirs.— The    method    of   measuring  dis- 
charge which  is  most  popular  among  the  irrigators  of  the  West 
because  of  its  simplicity  is  by  means  of  weirs.     This  method  is 
best  suited  to  streams  and  canals  of  moderate  size,  while  the 
results  are  generally  quite  accurate.      It  is  exclusively  used  in 
Australia,  and  is  extensively  employed  in  Colorado  and  other 
portions  of  the  West.     Where  the  contraction  is  complete  its 
coefficient  remains  constant,  and  the  Francis  formula  gives  the 
discharge  with  errors  not  exceed'ng  one  half  of  one  per  cent 
for  depths  of  water  varying  between  3  and  24  inches,  providing 
the  length  of  the  weir  is  not  less  than  three  or  four  times  the 
depth  of  the  water  flowing  over  it.     The  three  forms  of  weir 
which  are  most  popular  are  the  rectangular  weir  with  vertical 
sides,  and   the  trapezoidal  or  v  weir,  both  of  which  have   in- 
clined sides  with  slopes  of  about  one  fourth  horizontal  to   one 
vertical.     The  discharge  of  the  weir  Q  is  equal  to  the  product 
of  its  area  A  into  its  mean  velocity  v  ;  thus  Q  —  Av. 

85.  Rectangular  Measuring  Weir. — In  using   the   ordi- 
nary weir,  Fig.  6,  this  should  be  placed  at  right  angles  to  the 


FIG.  6.-— RECTANGULAR  MEASURING  WEIK. 

stream,  with  its  up-stream  face  in  a  vertical  plane.  The  crest 
and  sides  should  be  chamfered  so  as  to  slope  downward  on  the 
lower  side  with  an  angle  of  not  less  than  30°,  while  the  crest 
should  be  practically  horizontal  and  the  ends  vertical.  The 
dimensions  of  the  notch  should  be  sufficient  to  carry  the  entire 
stream  and  yet  leave  the  depth  of  water  on  the  crest  not  less 
than  five  inches.  The  sectional  area  of  the  jet  should  not 


58  FLO  W  AND  MEASUREMENT  OF    WATER. 

exceed  one  fifth  that  of  the  approaching  stream.  In  order 
that  the  proper  proportion  of  the  area  of  the  notch  to  that  of 
the  jet  shall  be  maintained,  central  contractions  may  be  in- 
troduced, dividing  the  weir  crest  into  several  orifices. 

86.  Francis'  Formulas.  —  The  form  of  equation  indicated 
by  theory  is 

Q  =  clh\, 

where  /  is  the  effective  length  of  the  weir  in  feet,  and  h  the 
depth  in  feet  of  water  flowing  over  it.  Because  of  the  down- 
ward curve  of  the  water  after  passing  over  the  weir,  this  height 
h  must  be  measured  at  some  distance  above  the  weir  in  order 
to  be  free  from  its  influence.  The  constant  c  is  a  coefficient 
which,  according  to  the  experiments  of  Mr.  J.  B.  Francis,  was 
determined  to  be  3.33.  Owing  to  this  falling  away  of  the 
crest  and  to  the  contraction  at  the  ends,  if  I'  be  the  effective 
length  of  the  weir,  one  end  contraction  makes  l'=(l—o.\k}, 
and  any  number  of  end  contractions  make  /'  =  (/  —  o.in/i). 
The  reduction  of  volume  by  the  crest  contraction  can  be  com- 
pensated for  by  the  coefficient  m,  and  inserting  these  factors 
in  the  ordinary  formula  of  discharge, 


we  have 

Q  =  \m  V2g(l  —  o.i  «//)//*. 

The  factors  \m  and  2g  are  constants,  and  representing  them 
by  c  we  can  substitute  it  in  the  formula  as  a  coefficient.  This 
is  the  coefficient  which  was  determined  to  be  equal  to  3.33  by 
Francis'  experiments,  and  substituting  this  value  and  trans- 
posing we  get  m  =  .622.  Substituting  these  values  into  the 
former  equation  and  eliminating,  we  get  for  approximate 
results, 


which  is  Francis'  formula. 

87.  Conditions    of   using    Rectangular   Weir.—  If    the 

weir  be  placed  so  as  to  meet  the  following  conditions,  a  more 


TRAPEZOIDAL    WEIRS.  59 

simple  formula  than  that  just  given  can  be  employed  for  ordi- 
nary use  :  thus  we  may  say 

Q  =  3-33#«. 

The  conditions  are,  that  the  water  shall  not  exceed  24  or 
be  less  than  4  inches  in  depth  ;  that  the  depth  on  the  crest 
shall  not  exceed  one  third  the  length  of  the  weir ;  that  there 
shall  be  complete  contraction  and  free  discharge ;  and  that 
the  water  shall  approach  without  perceptible  velocity  or  cross- 
currents. To  obtain  these  conditions  the  distance  from  the  side 
walls  to  the  crest  should  be  at  least  equal  to  the  depth  on  the 
weir,  and  the  distance  of  the  crest  above  the  bottom  of  the  chan- 
nel should  be  at  least  twice  the  depth  of  water  flowing  over  it. 
Air  should  have  free  access  under  the  falling  water,  and  the  ap- 
proaching channel  should  be  much  larger  than  the  weir  opening. 

Table  IX,  on  the  next  page,  is  adapted  from  L.  G.  Carpenter 
on  the  Measurement  of  Water. 

88.  Trapezoidal  Weirs. — As  a  result  of  experiments  made 
in  Italy  in  1886  by  Cippoletti,  he  adopted  a  trapezoidal  weir 
the  sides  of  which  have  an  inclination  of  one  fourth  horizontal 
to  one  vertical.  The  conditions  called  for  in  placing  a  rectan- 
gular weir  must  be  nearly  fulfilled  with  a  trapezoidal  weir,  but 
the  distance  of  the  sill  of  the  weir  from  the  bottom  of  the 
canal  must  be  at  least  three  times  the  depth  of  the  weir,  and 
its  length  must  be  at  least  three  times  the  depth  of  the  water 
flowing  over  it.  In  using  this  form  of  weir  the  equation  be- 
comes : 

Q  =  3.36V/A 

This  weir  seems  to  possess  some  excellent  qualities,  the  chief 
difficulty  in  connection  with  it  being  the  same  as  arises  in 
using  the  rectangular  weir,  namely,  that  where  silt-laden  water 
is  employed  this  may  fill  up  above  the  front  board  of  the  weir. 
In  using  a  triangular  weir  a  convenient  formula  has  been 
found  to  be  the  following : 

Q  =  2.65/A*, 


6o 


FLOW  AND  MEASUREMENT  OF    WATER. 


TABLE  IX. 

DISCHARGE  OVER  RECTANGULAR  WEIRS  OF  VARIOUS  LENGTHS, 
WITH  VARIOUS  DEPTHS  OF  WATER  AND  TWO  COMPLETE 
CONTRACTIONS. 

Formula,  Q  =  3-33^  —  o.2/fc)l 


Depth  from 
Still  Water 

Discharge  (?,  i 

n  Second-feet. 

Cor.  to  be 
added  to  give 

on  Crest,  in 
feet  =  h. 

/  =  I  ft. 

/  =  2  ft. 

/  =  5  f  I- 

/  =    10  ft. 

Q,  with  no 
contraction. 

.10 

.15 

.20 

•25 
•30 

•  35 

AO 

.1033 

.1879 
.2861 

•3959 
.5M9 
.6420 

.2078 
.3816 

.5843 
.8126 
1.0725 

1.3423 
I  .  6  i  60 

.5240 
.9627 

1.4787 
2.0227 

2.7057 
3.4032 
4-  ^89 

I.OSlg 
I.93I2 
2  .  9690 
4.1462 

5-4441 
6.8547 

8.  36=1; 

.0021 
.0058 
.0119 
.0208 
.0328 
.0483 
.  0674 

ic 

i  .9221 

4.9410 

9.9725 

.0905 

.  CQ 

2.  2392 

5.7748 

ii  .6672 

.1178 

e  e 

2    C.6Q8 

6.  6489 

13.4474 

.  1496 

60 

2.9128 

7  .  5607 

15.  3072 

.  18^9 

65 

3  .  2663 

8  .  5064 

17  .  2399 

.2271 

.70 

3.6313 

9.4882 

19.2497 

•2733 

•  75 

4.0052 

10.  ROO2 

21  .3252 

.3248 

80 

A      7884 

II  -5434 

23.4684 

.3816 

.85 

4.78O6 

I2.6I35 

25  .6790 

.4440 

.00 

13.7177 

27.9477 

.5123 

.QC 

14.8451 

30.2766 

.5864 

.OO 

I6.OOOO 

32.6667 

.6667 

•°5 

17.1784 

35  .  1099 

.7531 

.  10 

18.3825 

37.61  10 

.8460 

1C 

19,5080 

40.  1615 

•9455 

.20 

20.8569 

42.7654 

.0516 

2C 

22.  1269 

45  .4184 

.1646 

.  3O 

23.4189 

48.  1224 

.2846 

.  35 

24.7318 

50.8753 

.4117 

4.O 

26   0625 

C-3  .671O 

5460 

42 

27.4122 

56      5122 

.6878 

.  50 

28.7814 

59    3QQQ 

.8371 

.  55 

30.1675 

62.3290 

.0940 

60 

31  .  5727 

65  .  3OJ.2 

2.  1588 

65 

32  .Q935 

68  .3185 

2.  3315 

7O 

34.4269 

71  .  3710 

2  .  5  1  2O 

.  75 

35.8827 

74.4662 

2  .  70O8 

80 

37.  352O 

77  6020 

2    8980 

85 

38.8341 

80.  7716 

3.  IO34 

.00 

40.3321 

83.9816 

3.  3174 

QC 

41  .8436 

87.2271 

3.  53QQ 

•  V3 
2    OO 

43.3665 

90.5061 

3-771 

2    5O 

125.  16 

6.  ^q 

3OO 

162.70 

IO    3Q 

in 


MEASUREMENT   OF   CANAL    WATER.  6 1 

which  t  is  the  tangent  of  half  the  angle  in  the  notch  of  the 
triangle.     If  the  triangle  be  right-angled,  this  formula  becomes 

Q  =  0.3 1  ;#, 

which  is  one  of  the  simplest  formulas  that  can   be  used,  and 
gives  excellent  results  on  small  streams. 

89.  Weir  Gauge  Heights.— In   order   to    determine   the 
depth  of  water  flowing  over  the  weir  a  post  should  be  set  in 
the  stream  a  short  distance  above  it,  and  on  this  a  gauge  rod 
suitably  marked  should  be  attached.     For  very  exact  measure- 
ments a  hook  gauge  has  been  employed,  which  consists  of  a  hook 
attached  to  a  sliding  rule  fastened  or  hung  so  that  its  point  shall 
be  below  the  surface  of  the  water.     By  turning  a  tangent  screw 
the  hook  can  be  raised  until  it  is  exactly  level  with  the  surface, 
thus  giving  an  accurate  measurement  of  the  depth  of  water. 

90.  Measurement  of  Canal  Water. — No  method  has  as 
yet  been  devised  by  which  water  flowing  in  open  channels  can 
be   cheaply  and  conveniently  measured.     In  order  that  canal 
water  may  be  sold  by  quantity  it    is  necessary  that  the  volume 
admitted  to   the  canal   should   be   readily  ascertained   at  any 
time,  and  that  the  method  of  admission  should  be  so  regulated 
that  it  cannot  be  tampered  with.     As  no  method  has  yet  been 
devised    for   easily   and    cheaply  accomplishing  this,  water  is 
almost  universally  disposed  of  by  canal  owners  by  some  means 
.other   than  its  direct    sale   by  quantity.     It    is   customary  in 
India  to  charge  a  land  rental  which  is  regulated  in  accordance 
with  the  character  of  crop,  as  on  this  is  dependent  the  amount 
of  water  used.     In  our  country  water  rentals  are  charged  per 
acre  irrigated  rather  than  by  the  amount  of  water  required  in 
this  irrigation.     In   other  words,  water  is  not  sold  as  it  should 
be,  like  other  commodities  which  have  an  instrinsic  value,  by 
the  yard,  pound,  or  gallon,  though  such  would  unquestionably 
be  the  most  satisfactory  method  of  disposing  of  it,  both  to  the 
vendor  and  the  user.     Various  endeavors  have  been  made  to 
devise  some  cheap  and  convenient  method  of  measuring  water 
at  a  cost  commensurate  with  its  value,  but  none  of  these  can 
as  yet  be, said  to  have  achieved  success. 


62  FLOW  AND   MEASUREMENT  OF    WATER. 

91.  Methods  of  Measurement. — In    Italy   and   in  some 
other  portions  of  southern   Europe  a  "  module  "  or  measuring 
apparatus  has  been  employed  with  some  success  for  the  meas- 
urement of  canal  water.     This  module   consists  essentially  of 
inserting  in  the  canal   bank  a  regulating   gate  on  which  the 
height  of  head  can  be  maintained.     The  size  of  the  orifice  being 
known,  the  amount  of  water  passing  through  it  can  be  at  any 
time   ascertained.     Modifications  of  this  module  are  employed 
to  a  limited   extent  in  India  and  to  a  greater  extent  in  the 
United   States.     The  unit  of  measure  commonly  employed  in 
America  and  Italy  is  the  "  miner's  "  or  statute  inch,  though  the 
better  unit   is  the  second-foot     In  India  the  amount  of  water 
flowing  in  canals  and  distributaries  is  measured  either  by  a 
gauge  rod  placed  in  some  smooth  portion  of  the  channel,  as  in  a 
masonry  lined  aqueduct,  while  floats  are  timed  for  a  given  length 
in  the  aqueduct ;  or  by  means  of  a  V-shaped  measuring  weir. 

In  the  West  the  ordinary  module  employed  for  measuring 
the  miner's  inch  is  a  box  flume  closed  by  a  lifting  gate,  in 
which  case  the  head  above  the  orifice  is  changeable  and 
the  amount  passing  through  is  indeterminate.  Sometimes  a 
modification  of  this  module  devised  by  A.  D.  Foote  is  used, 
whereby  the  head  over  the  orifice  can  be  maintained  with  some 
degree  of  certainty.  None  of  these  modules  are  satisfactory, 
however,  for  the  measurement  of  large  volumes  of  water.  The 
measuring  Weir  is  in  all  probability  the  most  satisfactory 
method  yet  devised  of  obtaining  an  accurate  measure  of  the 
volume  of  water  passing  through  a  canal.  Where  water  passes 
through  pipes,  some  of  the  standard  varieties  of  water  meters 
can  be  employed  ;  or  if  these  are  considered  too  expensive,  some 
modification  of  them,  such  as  those  employed  on  the  Allesandro 
tract  in  California,  may  prove  satisfactory.  (Art.  217.) 

92.  The  Statute  Inch  or  Module. — As  already  stated,  the 
statute  inch  is  a  variable  quantity,  depending  on  its  designation 
in  different  States.     As  an  example,  the  statute  inch  of  Colo- 
rado (Art.  58)  is  defined  as  follows  :  An  inch-square  orifice  shall 
be  under  a  5-inch  pressure,  measured  from  the  top  of  the  orifice 
to  the  surface  of  the  water,  in  a  box  set  in  the  banks  of  the  ditch. 


FOOTERS    WATER   METER.  63 

This  orifice  shall  in  all  cases  be  6  inches  perpendicular  inside 
measurement,  and  all  slides  closing  the  same  shall  move  hori- 
zontally, while  from  the  water  in  the  ditch  the  box  shall  have  a 
descent  greater  than  one  eighth  of  an  inch  to  the  foot. 

93.  Foote's  Water  Meter. — This  apparatus  is  extensively 
used  on  the  canals  in  Southern  Colorado  and  on  some  of  the 
canals  in  Idaho  for  the  measurement  and  distribution  of  water 
by  the  inch.  It  acts  both  as  a  distributary  head  to  minor 


FIG.  7.— FOOTE'S  MEASURING  WEIR,  A.     WATER  Division,  B. 

channels  and  as  a  module  or  measuring  box.  It  is  constructed 
of  wood,  its  chief  merit  consisting  in  that  it  renders  it  possible 
to  maintain  very  nearly  the  standard  head  prescribed  by  statute 
over  the  opening.  As  shown  in  Fig.  7,  A,  it  consists  of  a  flume 
placed  in  the  main  lateral  A.  and  of  a  side  flume  B,  in  which  is 


64  FLO W  AND   MEASUREMENT  OF    WATER. 

constructed  the  measuring  gate,  while  opposite  to  it  is  a  long 
overfall  C,  the  height  of  which  is  such  as  to  maintain  a  stand- 
ard head  above  the  measuring  slot.  Such  a  weir  is  cheaply 
constructed  and  easily  placed  in  position,  while  its  cost  is  but 
trifling.  Its  chief  fault  as  at  present  constructed  is  the  fact 
that  it  measures  water  by  the  inch  instead  of  by  the  second- 
foot,  while  like  all  such  similar  devices  it  can  only  be  used  in 
moderately  small  channels,  since  the  difficulty  of  handling  a 
slot  on  a  large  stream  would  be  insurmountable. 

94.  Rating  Flumes. — Under  the  laws  of  the  State  of 
Colorado  rating  flumes  are  constructed  by  the  owners  of  private 
channels  for  the  measurement  of  the  flow  of  water,  while  the 
State  Engineer  is  directed  to  compute  the  amount  of  water  pass- 
ing through  them  at  various  stages.  They  offer  a  convenient 
means  of  ascertaining  the  amount  of  water  flowing  in  laterals 
and  distributaries  at  various  depths.  They  consist  of  a  simple 
open  flume  which  is  placed  in  a  straight  portion  of  the  channel 
a  few  hundred  yards  below  its  head  gate.  They  are  of  even 
width  with  the  channel,  on  the  same  grade,  and  their  sides  are 
sufficiently  high  to  carry  the  amount  of  water  likely  to  enter. 
For  channels  exceeding  6  feet  in  width  an  apron  and  wings  of 
one-inch  plank  are  built  for  7  feet  above  and  below  the  flume. 
The  latter  is  generally  16  feet  in  length,  consisting  of  a  framing 
of  6  by  6  scantling,  placed  4  feet  apart  and  lined  with  one-inch 
or  two-inch  plank. 

After  these  flumes  have  been  constructed  and  placed  the 
engineer  rates  them  by  means  of  a  current  meter,  and  furnishes 
the  Water  Commissioner  and  owner  of  the  private  channel  with 
a  table  showing  the  quantities  of  water  which  will  flow  through 
them  at  various  depths.  It  is  then  only  necessary  to  raise  the 
head  gate  until  the  desired  depth  flows  through  the  flume,  when 
the  gate  may  be  locked.  The  great  difficulty  with  this,  as 
with  any  similar  device,  is  the  changeability  of  head  in  the 
main  channel  above  the  head-gate  and  the  fluctuation  therein 
causing  a  change  in  the  volume  passing  through  the  flume,, 
necessitating  a  corresponding  change  in  the  position  of  the 
gate. 


DIVISORS— WORKS   OF  REFERENCE:   HYDRAULICS.        65 

95.  Divisors. — Another  method  of   distributing  water   to 
consumers  is  that  by  means  of  a  dividing  box,  the  object  of 
which  is  to  give  each  consumer  a  definite  portion  of  the  water 
flowing  in  the   lateral.     The   difficulty  of  dividing  the  water 
into  two    or  more  equal  parts  arises  from    the  fact  that  the 
water  has  not  a  uniform  velocity  across  the  entire  channel.     If 
therefore  equal  openings  be  made  across  a  channel,  those  near 
the  centre  have  the  greater  discharge.     As  a  consequence  the 
use  of  a  divisor  gives  only  approximate  results.     A  simple  form 
of  divisor  is  that  shown  in  Fig.  7,  B.     In  this  there  is  a  mov- 
able partition  A,  which  can  be  slid  out  into  the  main  channel 
so  as  to  give  the  amount  of  water  required  in  the  branch.     In 
order  to  maintain  an  equal  velocity,  the  water  is  brought  to  a 
state   of  approximate  rest   by  a  weir  board   a  few   inches  in 
height,  the  crest  of  which  is  sharp  on  the  up-stream  side. 

96.  Works  of  Reference.     Hydraulics. 

CARPENTER,   L.  G.     Measurement   and    Division   of   Water.     Bulletin 

No.  13,  State  Agricultural  College.     Fort  Collins,  Col.,  1891. 
CHURCH,  IRVING  P.     Mechanics  of  Engineering:  Fluids.     John  Wiley 

&  Sons,  New  York. 
FANNING,  J.  T.     Hydraulic  and  Water-supply    Engineering.     D.  Van 

Nostrand  &  Co.,  New  York,  1890. 
FLYNN,  P.  J.     Irrigation  Canals  and  Other  Irrigation  Works,  and  Flow 

of  Water  in  Irrigation  Canals.     Denver,  Col.,  1892. 
GREEN,   J.    S.     Fourth    Biennial    Report  State  Engineer  of  Colorado. 

Denver,  Col.,  1889. 
JOHNSON,  J.   B.     Theory  and    Practice  of   Surveying.     JoHn    Wiley  & 

Sons,  New  York,  1888. 
MULLINS,   Lieut. -Gen.  J.     Irrigation   Manual.     E.  &  F.  N.   Spon,  New 

York,  1890. 
POWELL,  J.  W.     Part  II,  nth  Annual  Report  U.  S.  Geological  Survey, 

1890. 
TRAUTWINE,  JOHN  C.     Engineers'  Pocket  Book.     John  Wiley  &  Sons, 

New  York,  1890. 
WEISBACH,  DuBois.    Hydraulics  and  Hydraulic  Motors.    John  Wiley  & 

Sons,  New  York,  1891. 

I 


PART   II. 

CANALS  AND   CANAL    WORKS. 


CHAPTER   X. 
CLASSES   OF   IRRIGATION   WORKS. 

97.  Gravity  and  Lift  Irrigation. — All  irrigation  works 
may  be  divided  into  these  two  great  classes.  Under  the  head 
of  gravity  or  natural-flow  irrigation  are  included  all  those 
works  in  which  the  water  may  be  conducted  to  the  land  by  the 
force  of  gravity  or  natural  flow.  They  include — 

1.  Perennial  canals ; 

2.  Periodical  and  intermittent  canals  ; 

3.  Inundation  canals 

4.  Storage  works ; 

5.  Artesian-water  supplies. 

6.  Subsurface  or  ground-water  supplies. 

Lift  irrigation  includes  those  forms  of  irrigation  in  which 
the  water  does  not  reach  the  land  by  natural  flow,  but  is  trans- 
ported to  it  by  pumping  or  other  means  of  lifting.  It  may  be 
divided  into  two  main  classes : 

1.  Irrigation  by  watering-pots,  hose,  or  sprinkling-carts; 

2.  Irrigation  by  pumping. 

The  first  needs  no  explanation ;  the  last  may  be  divided 
into  five  principal  classes : 

1.  Pumping  by  animal  power; 

2.  Pumping  by  water-wheels; 

3.  Pumping  by  windmills  ; 

4.  Lifting  by  elevators  ; 

5.  Pumping  by  steam-power. 

66 


SOURCES  OF  SUPPLY.  6/ 

The  sources  of  supply  for  all  forms  of  gravity  irrigation  are 
defined  by  the  titles  of  the  classes.  They  are  from  perennial 
streams,  intermittent  streams,  artesian  wells,  submerged  dams, 
tunnels  or  cuts,  or  by  the  storage  of  perennial,  intermittent,  or 
flood  waters.  The  sources  of  supply  for  lift  irrigation  may  be 
from  wells,  canals,  storage  works,  or  flowing  streams. 

98.  Navigation  and  Irrigation  Canals.— Canals  may  be 
used  for  irrigation  alone  or  for  irrigation  and  navigation  com- 
bined.    The  conditions  required  to  develop  an  irrigation  canal 
are :  first,  that  it  shall  be  carried  at  as  high  a  level  as  possible 
so  as  to  have  sufficient  fall  to  irrigate  the  land  to  a  considera- 
ble distance  on  both  sides  of  it ;  second,  it  should  be  fed  by  some 
source  of  supply  that  will  render  it  a  running  stream,  so  that 
the  water  used  in  irrigation  may  be  constantly  replaced  ;  third, 
it  should  have  such  a  slope  and  velocity  as  to  reduce  to  a  mini- 
mum  the   deposition  of  sediment   and  the  growth  of  weeds; 
fourth,  its  velocity  should  be  the  greatest  possible  in  order  that 
the  cross-section  may  be  reduced  to  a  minimum  for  a  given 
discharge.     On  the  other  hand,  navigation  requires  of  a  canal ; 
first,  that  the  water  in  it  shall  be  as  nearly  still  as  possible,  so 
that  navigation   may  be  equally  easy  in  both  directions ;  and, 
second,  it  requires  no  further  supply  of  water  than  is  necessary 
to  replace  the  loss  by  evaporation  and  absorption,  and  at  the 
points  of  transfer  from  higher  to  lower  levels.     It  is  thus  seen 
that  the  requirements  of   the  two  classes  are  conflicting,  and  it 
is  not  deemed  good  practice  to  make  irrigation  canals  for  pur- 
poses of  navigation. 

99.  Sources  of  Supply. — The  climate,  geology,  and  topog- 
raphy are  the  chief  factors  in  deciding  the  class  of  work  which 
belongs  to  a  given  region.     Where  the  precipitation  is  small, 
occurring  during  a  short  period  of  the  year,  and  resulting  in  the 
intermittent  or  periodical    flow  of  the  streams,  canals  of  this 
class  or  storage  works  must  be  employed.     Intermittent  and 
periodical   canals   are   usually  very  small   in   dimensions,  com- 
manding relatively  small  areas  of  land,  and  are  generally  env 
ployed  by  individual  farmers  for  the  utilization  of  the  waters 
of  some  stream  which  may  be  safely  counted  upon  for  a  tern- 


68  CLASSES  OF  IRRIGATION    WORKS. 

porary  supply  during  a  few  occasional  spring  storms  or  the 
melting  of  the  mountain  snows.  They  can  only  be  used  with 
safety  where  the  precipitation  is  nearly  sufficient  for  the  culti- 
vation of  crops  and  the  little  water  which  they  supply  is  of 
value  in  helping  this  out.  Storage  works  receive  their  supply 
from  intermittent  streams  carrying  moderate  volumes  of  water 
at  flood  times,  or  perhaps  from  perennial  streams,  artesian 
wells,  or  in  fact  from  any  source  from  which  a  permanent  sup- 
ply of  water  may  be  obtained.  Inundation  canals  are  used 
almost  exclusively  in  India  and  Egypt,  and  derive  their  supply 
from  streams  the  beds  of  which  are  at  an  altitude  relatively 
high  compared  with  the  surrounding  country.  This  is  the 
case  of  the  river  Indus,  which  practically  flows  on  a  ridge ;  and 
it  is  simply  necessary  when  the  water  in  this  river  is  high  to 
make  a  cut  through  its  banks,  and  thus  permit  it  to  flow  out  into 
the  canals  which  take  it  over  the  surrounding  country.  These 
inundation  canals  are  thus  supplied  by  flood  waters  which  flow 
above  the  general  level  of  the  surrounding  country,  and  rarely 
require  any  permanent  headworkto  control  the  entrance  of  the 
water  to  the  canal. 

Artesian  wells  derive  their  supplies  from  .artesian  water 
sources,  which  have  their  origin  usually  at  some  great  distance 
and  at  an  altitude  considerably  higher  than  the  outlet  of  the 
well.  Subsurface  cuts,  tunnels,  and  wells  derive  their  supply 
from  the  seepage  water  with  which  the  soil  in  nearly  every 
country  is  permeated. 

100.  Perennial  Canals. — Perennial  canals  derive  their 
supply  from  perennial  streams  or  from  storage  reservoirs.  They 
may  be  divided  into  two  classes,  according  to  the  location  of 
their  headworks.  These  are : 

1.  Highline  canals,  and 

2.  Low-service  or  deltaic  canals. 

Highline  canals  are  generally  of  moderate  size,  and  are  designed 
to  irrigate  lands  of  limited  area  which  lie  close  under  the  foot 
of  the  higher  hills.  They  are  generally  given  the  least  possible 
slope,  in  order  that  their  grades  may  remain  high  and  command 
the  greatest  amount  of  land.  In  such  canals  it  is  necessary  to 


DIMENSIONS  AND    COST  OF  SOME   PERENNIAL    CANALS.   69 

locate  the  headworks  high  up  on  the  stream,  frequently  in 
rocky  canyons  where  the  first  portions  of  the  line  may  en- 
counter heavy  and  expensive  rock  work.  Low-service  canals 
are  constructed  where  the  majority  of  the  lands  are  situated  in 
low-lying  and  extensive  valleys  and  where  the  location  of  the 
head  of  the  canal  depends  not  so  much  on  its  being  at  a  rela- 
tively high  altitude  and  commanding  a  great  area  as  upon  the 
suitability  of  the  site  for  purposes  of  diversion.  Highline 
canals  are  more  frequently  constructed  where  the  water  supply 
is  abundant  and  it  is  desirable  to  obtain  the  largest  amount  of 
land  to  which  to  apply  it.  Low-service  canals  are  constructed 
where  the  irrigable  lands  exceed  in  area  the  amount  of  water 
available. 

Deltaic  canals  have  been  constructed  chiefly  in  Egypt  and 
India  at  the  deltas  of  some  of  the  great  rivers,  as  the  Nile, 
Ganges,  Orissa  and  others.  They  are  essentially  low-service 
canals  and  are  built  in  regions  where  the  slope  is  very  small. 
As  a  consequence  their  cross-section  must  be  relatively  large, 
that  they  may  carry  a  given  discharge  with  the  least  velocity. 
They  are  usually  navigable  canals,  and  in  most  cases  the  water 
supply  is  abundant. 

101.  Dimensions  and  Cost  of  some  Perennial  Canals.— 
In  table  X,  on  page  70,  are  given  the  dimensions,  including  the 
capacity  and  area  commanded,  and  the  cost  in  various  terms 
of  some  of  the  great  perennial  canals  of  the  world. 

102.  Parts  of  a  Canal   System. — The   machinery  of  a 
great  perennial  canal  consists  essentially  of  the  following  parts, 
which  are  treated  here  in  the  order  given : 

1.  Source  of  supply  ; 

2.  Irrigable  lands ; 

3.  Main  canal ; 

4.  Head  and  regulating  works  ; 

5.  Control  and  drainage  works  ; 

6.  Distributaries  and  laterals. 

The  principal  units  of  this  system  are  the  main  canals  and  dis- 
tributaries. Between  different  canal  systems  the  greatest  points 
of  difference  are  found  in  the  headworks  and  in  the  first  few 


CLA  SSES   OF  I R  RIG  A  TION    WORKS. 


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PARTS   OF  A    CANAL    SYSTEM.  7 1 

miles  of  diversion  line,  where  numerous  difficulties  are  fre- 
quently encountered,  calling  for  variations  in  the  form  and  con- 
struction of  drainage  works  and  canal  banks. 

The  headworks  consist  usually  of  the  diversion  weir  with 
its  scouring  sluices,  of  the  head  regulating  gates  at  the  canal 
entrance,  and  of  the  head  or  first  escape  gates.  The  control 
works  consist  of  regulating  gates  at  the  head  of  the  branch 
canals,  and  of  escapes  on  the  line  of  the  main  and  branch 
canals.  The  drainage  works  consist  of  inlet  or  drainage  dams, 
flumes  or  aqueducts,  superpassages,  inverted  siphons,  and 
drainage  cuts.  In  addition  to  these  works  there  are  usually 
constructed  falls  and  rapids  for  neutralizing  the  slope  of  the 
country,  and  tunnels,  cuttings,  and  embankments.  Modules  or 
some  form  of  measuring  box  or  weir  are  necessary  for  the 
measurement  of  the  discharge. 


CHAPTER    XL 
ALIGNMENT,  SLOPE,  AND  CROSS-SECTION. 

103.  Location  of  Headworks. — The  headworks  of  a  canal 
are  almost  invariably  located  high  up  on  the  supplying  stream, 
in  order  to  command  a  sufficient  area  and  to  tap  the  stream 
where  the  water  is  clear  and  contains  the  least  amount  of  silt. 
By  so  locating  the  headworks  it  is  usually  possible  (owing  to 
the  greater  slope  of  the  country)  to  reach  the  water-sheds  or 
interfluves  with  the  shortest  possible  diversion  line.     The  dis- 
advantages of  this  class  of  location  are  serious,  since  the  canal 
line  is  sure  to  be  intersected  by  hillside  drainage,  the  passage 
of  which  entails  great  difficulties ;  and  as  the  adjacent  slopes 
of  the  country  are  heavy-,  much  expensive  hillside  cutting  is 
required. 

104.  Diversion  Line. — By  diversion  line  is  meant  that  por- 
tion of  the  canal  line  which  is  required   in  order  to  bring  it 
to  the  neighborhood  of  the  irrigable  lands.     It  is  that  waste 
construction  which  does  not  command  any  irrigable  land.     The 
endeavor  should  always  be  made  in  locating  the  canal  to  re- 
duce the  length  of  diversion  line  to  a  minimum,  so  that  the 
canal  shall  command  irrigable  land  and  derive  revenue  at  the 
earliest  possible  point  in  its  course. 

105.  Relation  between  Lands  and  Water  Supply. — In 
designing  an  irrigation  work  the  first  consideration  is  the  land 
to  be  irrigated.     The  projector  must  consider  the  area  of  this, 
its  nearness  to  market,  the  quality  of  the  soil,  the  climate,  and 
the  character  and  value  of  the  crops  which  it  will  produce.     In 

72 


SURVEY  AND   ALIGNMENT.  73 

addition,  the  value  and  ownership  of  the  land  must  necessarily 
be  considered.  All  of  these  quantities  having  been  satisfac- 
torily determined  and  the  necessity  of  supplying  water  for  irri- 
gation having  been  ascertained,  the  next  question  is  the  source 
of  supply  and  its  relative  location  to  the  lands.  This  supply 
may  be  found  in  some  adjacent  perennial  stream,  or  it  may  be 
necessary  to  transport  it  across  an  intervening  ridge  from  a 
neighboring  water-shed,  or  it  may  be  necessary  to  conserve  in 
storage  reservoirs  the  intermittent  flow  of  minor  streams.  The 
relation  of  the  water  supply  to  the  land,  the  extent  of  the  latter, 
and  the  volume  and  permanency  of  the  former  are  the  most  im- 
portant items  to  be  ascertained  in  the  preliminary  investigation 
of  any  irrigation  project. 

106.  Survey  and  Alignment. — Having  determined  the 
source  of  water  supply  and  its  relation  to  the  irrigable  lands, 
the  third  question  in  order  of  importance  is  the  alignment  of 
the  canal.  This  should  be  so  made  that  the  canal  shall  reach 
the  highest  part  of  the  irrigable  lands  with  the  least  length  of 
line  and  at  a  minimum  expense  for  construction.  The  line  of 
the  canal  should  follow  the  highest  line  of  the  irrigable  land, 
preferably  skirting  the  surrounding  foothills  and  passing  down 
the  summit  of  the  water-shed  dividing  the  various  streams. 

In  order  that  the  best  possible  alignment  may  be  obtained, 
careful  preliminary  and  location  surveys  are  necessary.  That 
all  possible  locations  may  be  examined,  it  is  desirable,  first,  to 
construct  a  general  topographic  map  on  some  large  scale, — 
perhaps  800  to  1500  feet  to  the  inch, — and  with  contour  lines 
showing  differences  of  elevation  of  from  5  to  10  feet.  On  such 
a  map  as  this  it  is  possible  to  at  once  lay  down  with  a  near  de- 
gree of  approximation  the  final  position  of  the  canal  line.  It 
is  also  frequently  possible  from  inspection  of  such  a  map  to 
save  many  miles  of  canal  by  the  discovery  of  some  low 
divide  or  some  place  in  which  a  short  but  deep  cut  or  a  tunnel 
will  save  a  long  roundabout  location.  Having  laid  down  this 
line  on  the  map,  the  final  location  may  be  made  on  the  ground, 
with  the  aid  perhaps  of  a  few  short  trial  lines  to  determine  its 
exact  position. 


74  ALIGNMENT,   SLOPE,  AND    CXOSS-SECTION. 

107.  Obstacles  to  Alignment. — Such  obstacles  as  streams, 
gullies,  ravines,  unfavorable  or  low-lying  soil  or  rocky  barriers 
are    frequently    encountered  in    canal   alignment.       The    best 
method  of  passing  these  must  be  carefully  studied.     It  may  be 
cheapest  to  carry  the  canal  around  these  obstructions,  or  it  may 
be  better  to  at  once  cross  them  by  aqueducts,  flumes,  or  inverted 
siphons,  or  to  cut  or  tunnel  through  the  ridges.     Careful  study 
should  be  made  of  each  case  and  estimates  made  of  the  cost 
not  only  of  first  construction,  but  of  ultimate  maintenance.     In 
crossing  swamps  or  sandy  bottom  lands  it  may  be  cheaper,  be- 
cause of  the  losses  which  the  water  will  sustain  from  evapo- 
ration and  absorption,  to  carry  the  canal  in  an  artificial  channel 
through  such    places.      If  water  be  abundant  it  may  be  less 
expensive  on  hillside  work  to  simply  build  the  canal  with  an 
embankment  on  its  lower  side,  permitting  the  water  to  flood 
back  on  the  upper  side  according   to  the  slope  of  the  country. 
In  such  cases  the  losses  by  evaporation   and  absorption  will  be 
great  in  the  beginning,  but  ultimately  these  flat  places  maybe- 
come  silted  up  and  a  permanent  channel  made  through  them. 
The  relative  cost  of   building  a  sidehill  canal  wholly  in  excava- 
tion or  partly  in  embankment  should  be  considered.     If  the 
hillside   is  steep   and  rocky,  the  advisability  of  tunnelling,  of 
building  a  masonry  retaining  wall  on  the  lower  side   of  the 
canal,  or  of  carrying  it  in  an  aqueduct  or  flume  will  have  to  be 
considered. 

108.  Sidehill  Canal  Work.— It  is  extremely  difficult    to 
carry  a  large  canal  along  steep  sidehill  slopes.     In  order  to  get 
a  sufficient  cross-section  to  carry  the  volume  required  without 
unduly  increasing  the  velocity  demands  the  exercise  of  careful 
judgment.     It  is  possible  to  get  the  same  cross-sectional  area 
by  employing  different  proportions  of  depth  to  bed  width.     The 
less  the  cross-sectional  area  of  a  channel,  the  less  its  cost  and 
the  expense  for  maintenance.     It  is  therefore  first  necessary  to 
choose  the  highest  possible  velocity  which  the  resistance  of  the 
material  and  the  necessity  of  commanding  land  will  permit, 
and  then  to  give   the  canal  such  a  cross-sectional  area  as  will 
produce  the  required  discharge.     The  great  difference  in  ex- 


CURVATURE.  75 

cavation  of  two  canals  of  equal  capacity  but  different  propor- 
tions of  bed  width  to  depth  is  graphically  shown  in  Fig.  8. 
In  one  case  many  times  the  amount  of  material  will  have  to  be 
removed  than  in  the  other,  while  the  surface  exposed  to  evap- 
oration and  absorption  is  greatly  increased.  Where  the  mar 


c 

FIG.  8. — CANAI.  CROSS-SECTIONS  FOR  VARYING  BED-WIDTHS. 

terialis  suitable  and  not  too  liable  to  cause  loss  by  percolation, 
it  is  well  to  equalize  the  cut  and  fill.  In  this  way  still  less 
material  will  have  to  be  moved,  for,  as  shown  in  the  illustration, 
the  depth  of  excavation  is  diminished  by  raising  the  lower  bank. 

109.  Curvature. — A  direct  or  straight  course  is  the  most 
economical,  as  it  gives  the  greatest  freedom  of  flow  and  causes 
the  least  erosion  of  the  banks.  It  also  greatly  diminishes 
the  cost  of  construction  and  the  losses  by  absorption  and 
evaporation  consequent  on  the  increased  length  of  a  less 
direct  location.  It  is  an  error  in  alignment  to  adhere  too 
closely  to  grade  lines  following  the  general  contour  of  the 
country.  By  the  insertion  of  an  occasional  fall  it  is  frequently 
possible  to  obtain  a  more  desirable  location  and  to  diminish 
the  cost  of  construction  by  the  avoidance  of  some  natural 
obstacle. 

One  of  the  most  serious  errors  in  alignment  is  the  careless 
location  of  curves,  to  which  detail  too  little  attention  is  ordi- 
narily paid.  The  insertion  of  sharp  bends  inevitably  results  in 
the  destruction  of  the  canal  banks,  or  requires  that  they  shall 
be  paved  or  otherwise  protected  to  prevent  their  erosion. 
Instances  have  been  noted  where  engineers  have  inserted 
great  curves  carefully  constructed  on  some  fixed  radius  of 
absurd  length,  as  though  the  canal  were  a  railway  line.  Curva- 
ture diminishes  the  delivering  capacity  of  the  canal,  and  too 


76  ALIGNMENT,  SLOPE,  AND    CROSS-SECTION. 

sharp  a  curve  endangers  the  structure  itself.  In  large  canals 
of  moderate  velocity  it  will  be  safe  in  most  cases  to  take  the 
radius  of  curvature  at  from  three  to  five  times  the  depth  of  the 
canal.  As  the  cross-section  becomes  smaller  or  the  velocity  is 
increased,  the  radius  of  curvature  should  be  correspondingly 
increased.  To  keep  up  the  discharge  of  a  canal  either  its 
cross-section  or  grade  should  be  increased  in  proportion  to  the 
sharpness  of  the  curve. 

1 10.  Borings,  Trial  Pits,  and  Permanent  Marks. — In 
finally  locating  an  expensive  work,  borings  and  trial  pits  should 
be  made,  the  former  with  a  light  steel  rod  and  the  latter  by 
simple  excavation  in  order  to  discover  the  character  of  the 
material  to  be  encountered.  In  making  the  final  survey  of  a 
canal  it  is  well  to  place  at  convenient  intervals  permanent 
bench  marks  of  stone  or  other  suitable  material.  The  estab- 
lishment of  these  along  the  side  of  the  canal  in  some  safe  place 
will  give  convenient  datum  points  to  which  levels  can  be  re- 
ferred whenever  it  may  be  necessary  to  make  repairs  or  run 
branch  lines.  Mile  or  quarter-mile  posts  or  permanent  stakes 
should  also  be  set  in  the  canal  banks  so  that  future  surveys 
and  changes  in  the  line  may  be  referred  to  these. 

in.  Example  of  Canal  Alignment — Ganges  Canal.— 
An  excellent  example  of  a  typical  alignment  on  one  of  the 
great  Indian  canals  is  that  of  the  Ganges  canal,  which  heads  in 
the  Ganges  river  at  Hurdwar,  where  the  stream  issues  sud- 
denly from  between  the  foothills  of  the  Himalayas  on  to  the 
broad  level  plains.  In  the  first  20  miles  of  its  course  the  canal 
encounters  considerable  sub-Himalayan  drainage,  and  the 
works  for  the  passage  of  this  and  for  the  reduction  of  slope 
in  the  canal  by  means  of  falls  are  important  (PI.  II).  The 
slope  of  the  river  bed  and  country  averages  from  8  to  10  feet 
per  mile. 

At  the  site  of  the  headworks  the  river  is  divided  into 
several  channels,  one  of  which,  about  3  feet  in  width,  follows 
the  Hurdwar  shore  and  rejoins  the  main  stream  half  a  mile 
below  that  town.  As  the  discharge  of  the  canal  is  6700  sec- 
ond-feet and  that  of  the  river  never  falls  below  8000  second- 


GANGES  CANAL.  77 

feet,  only  a  portion  of  the  water  is  required  at  any  time.  This 
is  diverted  to  the  Hurdwar  channel  by  means  of  training 
works  and  temporary  bowlder  dams,  and  the  current  has  deep- 
ened the  channel  until  it  now  has  a  uniform  slope  of  7^  feet 
per  mile  to  the  canal  head.  The  regulator  is  about  half  a  mile 
below  the  first  training  works,  and  consists  of  a  weir  and  scour- 
ing sluices  across  the  channel.  In  the  first  few  miles  the  canal 
crosses  several  minor  streams  which  are  admitted  by  means  of 
inlets.  At  the  sixth  mile  it  is  crossed  by  the  Ranipur  torrent, 
which  is  passed  over  it  in  a  masonry  superpassage  195  feet 
in  breadth  (PL  XVI).  In  the  tenth  mile  the  Puthri  torrent, 
having  a  catchment  basin  of  about  80  square  miles,  or  twice 
that  of  the  Ranipur,  is  carried  across  the  canal  by  a  similar 
superpassage  296  feet  in  breadth.  The  sudden  flood  dis- 
charges in  these  torrents  are  of  great  violence,  the  Puthri 
discharging  as  much  as  15,000  second-feet  and  having  a  velocity 
of  about  15  feet  per  second. 

In  the  thirteenth  mile  the  canal  encounters  the  Rutmoo 
torrent  (Article  183),  which  has  a  slope  of  8  feet  per  mile  and  a 
catchment  basin  half  as  large  again  as  that  of  the  Puthri.  This 
torrent  is  admitted  into  the  canal  at  its  own  level,  and  in  the 
side  of  the  canal  opposite  to  the  inlet  is  an  open  masonry  out- 
let dam  or  set  of  escape  sluices.  Just  below  this  level  crossing 
is  a  regulating  bridge  by  which  the  discharge  of  the  canal  can 
be  readily  controlled  ;  thus  in  time  of  flood,  by  opening  the 
sluices  in  the  outlet  dam  and  adjusting  those  in  the  regulator 
so  as  to  admit  into  the  canal  the  volume  of  water  required,  the 
remainder  is  discharged  through  the  scouring  sluices,  whence  it 
continues  in  its  course  down  the  torrent. 

In  the  nineteenth  mile,  near  Roorkee,  the  canal  crosses  the 
Solani  river  and  valley  on  an  enormous  masonry  aqueduct 
(Article  189).  The  Solani  river  in  times  of  highest  flood  has 
a  discharge  of  35,000  second-feet  and  the  fall  of  its  bed  is 
about  5  feet  per  mile.  The  total  leagth  of  the  aqueduct  is 
920  feet.  The  banks  of  the  canal  on  the  up-stream  side  are 
revetted  by  means  of  masonry  steps  for  a  distance  of  10,713 
feet,  and  on  the  down-stream  side  for  a  distance  of  2,722  feet. 


ALIGNMENT,   SLOPE,  AffD   CROSS-SECTION. 


TURLOCK  CANAL.  79 

For  if  miles  the  bed  of  the  canal  is  raised  on  a  high  embank- 
ment previously  to  its  reaching  the  aqueduct,  and  for  a  dis- 
tance of  half  a  mile  below  it  is  on  a  similar  embankment. 
The  greatest  height  of  the  canal  bed  above  the  country  is  24 
feet  (PL  XIV).  The  aqueduct  proper  consists  of  fifteen  arches 
of  50  feet  span  each.  In  addition  to  these  great  works  there 
are  in  the  first  20  miles  of  the  canal  five  masonry  works  for 
damming  minor  streams  and  a  number  of  masonry  falls. 

Beyond  Roorkee  the  main  canal  follows  the  high  divide 
between  the  Ganges  and  the  west  Kali  Nadi,  and  continues  in 
general  to  follow  the  divide  between  the  Ganges  and  the  Jumna 
rivers  to  Gopalpur,  a  short  distance  below  Aligarh,  where  the 
main  canal  bifurcates,  forming  the  Cawnpur  and  Etawah 
branches.  The  former  tails  into  the  Ganges  river  at  Cawnpur 
and  is  170  miles  in  length.  The  Etawah  branch  is  also  170 
miles  long  and  tails  into  the  Jumna  river  near  Humerpur.  The 
Vanupshahr  branch  leaves  the  main  line  at  the  fiftieth  mile, 
and  flows  past  the  towns  of  Vanupshahr  and  Shahjahanpur. 
It  formerly  terminated  at  mile  82^-,  emptying  into  the  Ganges 
river ;  but  it  is  now  continued  to  a  point  near  Kesganj,  where 
it  tails  into  the  Lower  Ganges  canal.  The  first  main  distribu- 
taries are  taken  from  both  sides  of  the  canal  a  short  distance 
below  Roorkee.  The  nature  of  the  country  offers  abundant 
facilities  for  escapes  from  the  canals,  of  which  five  are  con- 
structed on  the  main  line,  four  on  the  Cawnpur  branch,  and 
three  on  the  Etawah  branch,  besides  numerous  small  escapes 
to  the  distributaries. 

112.  Example  of  Canal  Alignment — Turlock  Canal.— 
A  typical  American  canal  alignment  is  that  of  the  Turlock 
canal,  which  is  diverted  from  the  Tuolumne  river  in  Cali- 
fornia at  a  point  where  it  emerges  from  the  Sierras  between 
high  rocky  canyon  walls.  For  the  first  5  miles  the  canal  is 
built  along  steeply  sloping  hillside,  and  it  crosses  numerous 
drainage  channels  in  its  endeavors  to  surmount  the  bluffs  bor- 
dering the  river  and  gain  the  irrigable  lands.  The  topography 
is  so  irregular  that  the  first  attempts  which  were  made  at  diver- 
sion were  unsuccessful.  The  present  location  was  discovered 


8o 


ALIGNMENT,   SLOPE,  AND    CROSS-SECTION. 


only  after  a  careful  detailed  topographic  map  had  been  made 
of  the  entire  region,  and  from  this  the  canal  line  was  laid 
down  (Fig.  9). 

The  headworks  of  the  Turlock  canal  consist  of  a  masonry 
dam  which  is  constructed  as  a  common  diversion  weir  for  the 


FIG.  9.— TURLOCK  CANAL.     PLAN  OF  DIVERSION  LINE, 


Turlock  canal  and  the  canal  of  the  Modesto  Irrigation  district, 
which  latter  heads  on  the  opposite  or  north  bank  of  the  river. 
This  weir  (Article  278)  is  located  between  high  canyon  walls, 
two  miles  above  the  town  of  La  Grange,  at  a  point  where  the 
abutments  and  foundation  of  the  weir  consist  of  firm  homo- 
geneous dioritic  basalt,  in  which  scarcely  any  excavation  is 
required.  The  canal  is  diverted  from  the  south  bank  of  the 


TURLOCK   CANAL. 


81 


river  at  a  point  about  50  feet  above  the  end  of  the  main  weir. 
Owing  to  the  great  floods  which  occur  in  this  narrow  canyon 
the  water  may  rise  as  much  as  15  feet  in  an  hour  and  the 
maximum  height  which  it  is  estimated  to  reach  above  the  sill 
of  the  canal  is  16  feet.  The  pressure  of  this  height  of  water 
on  the  regulator  head  would  be  so  great  as  to  materially  in- 
crease the  cost  of  its  construction.  Accordingly  the  canal 
heads  in  a  tunnel  560  feet  in  length,  blasted  through  the  rock 


FIG.  10. — TURLOCK  CANAL.     VIEW  OF  SIDEHILL  WORK. 


of  the  canyon  walls,  and  having  no  regulating  apparatus  at  its 
entrance.  Where  it  discharges  into  the  open  cut,  which  is  the 
commencement  of  the  canal,  regulating  gates  and  scouring  or 
escape  sluices  are  placed.  The  entrance  tunnel  is  12  feet  wide 
at  the  bottom,  5  feet  in  height  to  the  spring  of  the  arch,  above 
which  it  is  semicircular  with  a  6-foot  radius.  Its  slope  is  24 
feet  per  mile  and  it  is  excavated  in  a  firm  dioritic  rock  which 
requires  no  lining.  The  regulator  in  the  canal  head  below  the 
exit  of  the  tunnel  consists  of  six  gates,  each  3  feet  wide  in  the 
clear  and  12  feet  in  height.  These  gates  are  constructed  of 
timber  and  iron,  and  slide  on  angle-iron  bearings  let  into  the 
rock  and  firmly  set  in  concrete.  The  escape  is  set  at  right 


82 


ALIGNMENT,  SLOPE,  AND   CROSS-SECTION. 


angles  to  the  canal  line  heading  immediately  above  the  regu- 
lator, between  it  and  the  end  of  the  tunnel,  and  tailing  back 
into  the  Tuolumne  river  a  short  distance  below  the  subsidiary 
weir.  Like  the  regulator,  the  escape  consists  of  six  gates,  each 
3  feet  wide  in  the  clear,  12  feet  high,  and  constructed  of  simi- 
lar material  and  in  like  manner.  It  is  estimated  that  whereas 


FIG.  ii.— TURLOCK  CANAL.    VIEW  IN  TUNNEL. 

a  maximum  flood  of  16  feet  over  the  sill  of  the  tunnel  will  give 
a  discharge  in  front  of  the  regulator  and  escape  of  about  4000 
second-feet  with  a  velocity  of  20  feet  per  second,  the  wasting 
capacity  of  the  escape  will  be  at  least  6000  second-feet,  thus 
fully  insuring  the  canal  against  accident  from  this  source. 

Below  the  regulating  gates  the  main  canal  proper  begins, 
having  a  capacity  of   1500  second. feet.     For  the  first  6200  feet 


TURLOCK   CANAL.  83 

it  is  excavated  in  slate  rock  on  a  steep  hillside  (Fig.  10).  It 
has  a  bed  width  of  20  feet,  depth  of  water  10  feet,  the  upper 
rock  slope  being  ^  to  I,  while  the  lower  bank  or  downhill 
slope,  where  gullies  are  crossed,  is  built  up  with  an  inner  slope 
of  J-  to  I  and  is  faced  with  18  inches  of  dry-laid  retaining-wall 
inside  and  outside,  the  interior  of  the  bank  consisting  of  a  well- 
puddled  earth  core  12  feet  in  top  width  (Fig.  14).  Where  this 
portion  of  the  canal  is  on  ordinary  sloping  ground,  not  cross- 
ing gulches,  its  dimensions  are  the  same  but  the  inner  face 
only  has  the  18  inches  of  riprapping  the  downhill  slope  of  the 
bank  consisting  of  dirt  and  other  soil.  The  top  width  of  the 
bank  in  such  places  is  5  feet  and  the  puddle  wall  5  feet  in 
thickness.  This  portion  of  the  canal  line  has  a  grade  of  7.92 
feet  per  mile,  which  gives  a  velocity  of  7^  feet  per  second. 

At  the  end  of  this  slate-rock  work  the  canal  empties  into 
Snake  ravine,  up  which  the  water  of  the  canal  runs  for  940  feet. 
This  is  effected  by  constructing  an  earth  dam  across  the  mouth 
of  the  ravine  just  below  the  entrance  of  the  canal,  which  raises 
the  surface  of  the  water  so  as  to  form  a  small  settling  reservoir 
and  produces  a  flow  up  the  course  of  the  ravine  for  the  dis- 
tance above  mentioned.  The  earth  dam  is  20  feet  wide  on 
top,  318  feet  long  on  the  crest,  with  slopes  of  2  to  I  and  a 
maximum  height  of  52  feet.  This  dam  was  partly  constructed 
of  material  borrowed  from  its  abutments  and  the  canal  exca- 
vation and  partly  by  a  silting  process  from  material  washed 
out  of  a  hydraulic  cut  at  the  upper  end  of  the  ravine.  This 
hydraulic  cut,  which  is  utilized  as  the  canal  bed,  is  800  feet  in 
length  and  45  feet  in  maximum  height,  with  slopes  of  I  to  I 
and  a  grade  of  5  feet  per  mile.  Owing  to  the  abundance  of 
water  procurable  this  cut  was  more  cheaply  excavated  by  the 
hydraulic  process  than  it  could  have  been  by  other  means.  At 
the  far  end  of  the  cut  the  canal  enters  an  old  hydraulic  wash- 
ing which  is  utilized  for  its  channel  for  a  length  of  2380  feet, 
after  which  it  enters  a  rock  cut  860  feet  long,  with  a  maximum 
depth  of  45  feet  and  a  similar  cross-section  to  the  cut  first 
described. 

At  the  end  of  this  rock  cut  the  canal  water  is  discharged 


84  ALIGNMENT,  SLOPE,  AND   CROSS-SECTION. 

into  Dry  creek,  down  which  it  flows  for  a  distance  of  6500  feet 
on  a  grade  of  12  feet  to  the  mile,  and  from  which  it  is  diverted 
by  means  of  an  earth  dam  460  feet  long.  This  dam  has  a 
maximum  height  of  23  feet  with  side  slopes  of  3  to  I,  and  is 
riprapped  to  a  depth  of  3  feet  on  its  upper  face.  At  its  south 
end  the  dam  abuts  on  sandstone  rock  in  which  a  waste-way 
is  cut  50  feet  wide  with  its  sill  4  feet  below  the  crest  of 
the  dam,  and  which  will  discharge  back  into  the  creek  180  feet 
below  the  toe  of  the  dam.  Between  the  waste-way  and  the 
end  of  the  dam  is  a  waste-gate  which  it  is  intended  shall  be 
used  in  the  time  of  freshets,  for  Dry  creek  has  a  maximum 
discharge  of  4000  second-feet  and  as  the  freshets  are  quick 
and  violent  a  large  wasting  capacity  is  necessary.  These 
waste-gates  are  ten  in  number,  each  3  feet  wide  in  the  clear 
and  10  feet  in  depth.  They  fall  automatically  outward  or 
down-stream,  being  hinged  at  the  bottom  to  a  concrete  floor 
laid  on  the  bed-rock,  and  when  raised  they  are  attached  by 
chains  to  the  piers. 

For  about  a  mile  below  Dry  creek  the  canal  is  excavated 
in  heavy,  sandy  loam,  in  which  it  has  a  bed  width  of  30  feet, 
with  slopes  2  to  I,  a  depth  of  10  feet  and  a  grade  of  i£  feet 
per  mile.  At  the  end  of  this  excavation  the  canal  crosses  Dry 
creek  in  a  flume  62  feet  in  height  and  450  feet  long,  after 
crossing  which  the  canal  enters  a  series  of  three  tunnels,  the 
cross-sections  of  which  are  nearly  similar  to  that  of  the  first 
tunnel,  while  they  are  excavated  in  a  tufa  and  sandstone 
which  will  require  no  timbering.  The  first  tunnel  (Fig.  n)  is 
2ii  feet  in  length,  the  second  400  feet  and  the  third  400  feet 
in  length,  while  they  are  separated  by  short,  open  cuts  exca- 
vated in  hardpan  and  clay,  which  are  respectively  250  and  300 
feet  in  length.  The  last  tunnel  discharges  into  Delaney  gulch, 
which  is  crossed  by  constructing  a  high  bank  or  earth  dam 
below  the  canal,  the  total  length  of  which  is  180  feet,  its  maxi- 
mum height  being  40  feet  and  its  top  width  20  feet.  The 
volume  of  discharge  of  this  gulch  is  so  trifling  that  it  was 
unnecessary  to  provide  a  waste-way  or  escape  at  this  point. 
Immediately  after  crossing  the  gulch  the  canal  enters  a  cut  8 


SLOPE  AND  CROSS-SECTION.  85 

feet  in  maximum  depth,  with  the  same  cross-section  and  grade 
as  the  first  cut  and  having  a  length  of  3300  feet.  The  canal 
is  then  widened  to  a  bed  width  of  35  feet  and  depth  of  10  feet 
and  is  given  a  grade  of  i  foot  per  mile.  At  the  end  of  a  mile 
and  a  half  Peasley  creek  is  crossed  on  a  trestle  and  flume  60 
feet  in  height  and  360  feet  long,  the  water-way  on  which  is  20 
feet  wide  and  7  feet  in  depth.  This  flume  is  provided  with  an 
escape  constructed  in  its  bottom  and  discharging  into  two 
small  sloping  flumes  which  lead  the  water  down  into  the  bed 
of  Peasley  creek  (Article  168). 

At  the  end  of  the  flume  the  main  canal  is  reached  and 
traversed  for  a  distance  of  II  miles,  in  which  are  two  rock  cuts, 
each  3000  feet  long  and  respectively  20  and  30  feet  wide  on 
the  bottom,  depth  of  water  7^  feet  and  grade  5  feet  per  mile. 
The  remainder  of  this  length  of  the  canal  varies  in  cross-sec- 
tion according  to  the  soil,  but  most  of  it  has  a  bottom  width  of 
70  feet  and  depth  of  water  of  7^  feet,  slopes  2  to  I  and  a 
grade  of  I  foot  per  mile. 

The  main  canal  as  outlined  above  consists  for  the  18  miles 
of  its  length  of  a  purely  diversion  channel,  the  object  of  which 
is  to  bring  the  water  to  the  irrigable  lands  included  within  the 
area  of  the  Turlock  district.  At  the  terminus  of  this  diversion 
line  the  canal  begins  at  once  to  do  duty  by  watering  the  lands, 
and  below  this  point  the  main  line  is  divided  into  four  main 
branches,  each  of  which  has  a  bottom  width  of  30  feet,  depth 
of  water  5  feet,  and  grade  .of  2  feet  per  mile,  their  aggregate 
length  being  80  miles.  In  addition  to  these  main  branches 
minor  distributaries,  havingatotal  length  of  180  miles,lead  the 
water  to  each  section  of  land.  The  discharge  of  the  branches 
is  so  designed  as  to  give  a  uniform  velocity  of  2^  feet  per 
second,  in  order  that  any  matter  carried  in  suspension  will  be 
held  up  until  deposited  on  the  agricultural  lands  instead  of  in 
the  canals. 

113.  Slope  and  Cross-section. — These  two  quantities  are 
nearly  related  and  are  interdependent  one  upon  the  other. 
Having  determined  the  discharge  required,  the  carrying  capac- 
ity for  this  quantity  can  be  obtained  by  increasing  the  slope 


86  ALIGNMENT,  SLOPE,  AND    CROSS-SECTION. 

and  consequent  velocity  and  diminishing  the  cross-sectional 
area ;  or  by  increasing  the  cross-sectional  area  and  diminishing 
the  velocity.  The  determination  of  the  proper  relation  of 
cross-section  to  slope  requires  considerable  judgment.  If  the 
material  in  which  the  excavation  is  to  be  made  will  permit,  it 
is  well  to  give  a  high  velocity,  as  the  deposition  of  silt  and  the 
growth  of  weeds  are  thus  reduced  to  a  minimum.  A  steep 
slope  may  result,  however,  in  bringing  the  canal  to  the  irri- 
gable lands  at  such  an  elevation  that  it  will  not  command  the 
desired  area.  Again,  it  may  be  inadvisable  to  give  too  great 
a  cross-section  if  the  construction  is  in  sidehill  or  in  rock, 
of  other  material  which  is  expensive  to  remove.  Other  things 
being  equal,  the  correct  relation  of  slope  to  cross-section  is 
that  in  which  the  velocity  will  neither  be  too  great  nor  too 
slow,  and  yet  the  amount  of  material  to  be  removed  will  be 
reduced  to  a  minimum.  Where  the  fall  will  permit,  the  slope 
of  the  bed  of  the  main  canal  should  be  less  than  that  of  the 
branches,  which  should  be  less  than  that  of  the  distributaries 
and  laterals,  the  object  being  to  secure  a  nearly  uniform  veloc- 
ity throughout  the  system,  so  that  sedimentary  matter  carried 
in  suspension  may  not  be  deposited  until  the  irrigable  lands 
are  reached. 

114.  Limiting  Velocity. — In  order  that  the  proper  slope 
may  be  chosen,  one  which  will  produce  a  velocity  that  shall 
not  cause  silt  to  be  deposited  on  the  one  hand,  or  erode  the 
banks  on  the  other,  the  amount  of  such  velocities  for  different 
soils  should  be  known.  In  a  light,  sandy  soil  it  has  been  found 
that  a  surface  velocity  of  from  2.3  to  2.4  feet  per  second,  or 
mean  velocities  of  1.85  to  1.93  feet  per  second,  give  the  most 
satisfactory  results.  It  has  been  discovered  that  velocities  of 
from  2  to  3  feet  per  second  are  ordinarily  sufficiently  swift  to 
prevent  the  growth  of  weeds  or  the  deposition  of  silt,  and, 
other  things  being  equal,  this  velocity  is  the  one  which  it  is 
most  desirable  to  attain.  In  ordinary  soil  and  firm  sandy  loam 
velocities  of  from  3  to  3^  feet  per  second  are  safe,  while  in  firm 
gravel,  rock,  or  hardpan  the  velocity  may  be  increased  to  from 
5  to  7  feet  per  second.  It  has  been  found  that  brickwork  or 


EXAMPLES  OF  'CANAL    GRADES.  87 

heavy  dry-laid  paving  or  rubble  will  not  stand  velocities  higher 
than  1 5  feet  per  second,  and  for  greater  velocities  than  this  the 
most  substantial  form  of  masonry  construction  should  be  em- 
ployed. 

115.  Grades  for  Given  Velocities. — The  grade  required  to 
give    these    velocities   is  chiefly  dependent    on  the  cross-sec- 
tional area  of  the  channel.     Much  higher  grades  are  required 
in  small  than  in  large  canals  to  produce  the  same  velgcity. 
The  velocity  which  is  required  being  known,  the  grade  can  be 
ascertained  from  Kutter's  or  some  similar  formula.     In  large 
canals  of  60  feet  bed  width  or  upwards,  and  in  sandy  or  light 
soil,  grades  as  low  as  6  inches  in  a  mile  produce  as  high  veloci- 
ties as  the  material  will  stand.     In  more  firm  soil  this  grade 
may  be  increased  to  from  12  to  18  inches  to  the  mile,  whereas 
smaller  channels  will  stand  slopes  of  from  2  to  5  feet  per  mile, 
according  to  the  material  and  dimensions  of  the  channel. 

116.  Examples  of  Canal  Grades. — On  the  Ganges  canal, 
the  bottom  width  of  which  is  170  feet  and  the  depth  7  feet,  a 
slope  of  14  inches  per  mile  given  in  sandy  soil  produces  such  a 
velocity  that  the  current  just  ceases  to  cut  the  banks  or  to  de- 
posit silt,  showing  that  this  is  the  correct  slope  for  that  canal 
and  material.     In   another  portion   of  the  same  canal  slopes 
of    from    15    to    17    inches   have    been   found   too   great,  and 
much  damage  has  been  done  to  the  banks.     A  velocity  of  3 
feet  per  second  given  to  the  Soane  canals  is  found  too  great  for 
the  material,  as  much  damage  was  caused  by  erosion.     Care- 
ful observations  of  the  slope  on  the  Ganges  canal  show  that  a 
current  apparently  perfectly  adjusted  to  light,  sandy  soil  was 
produced  by  a  surface  velocity  of  about  2.4  feet  per  second,  or 
a  mean  velocity  of  about   1.9  feet  per  second.     In  one  of  the 
distributaries   in    sandy  soil   having  some    clay  in    it  a  mean 
velocity  of   1.93  feet  per  second  caused  slight  deposits  of  silt, 
but  did  not  permit  the   growth    of  weeds.     On   the  western 
Jumna  canal  silt  was  deposited  in  small  quantities  with  a  ve- 
locity of  from  2  to  2.75  feet  per  second,  while  in  sandy  soil  the 
latter  velocity  was  the  highest  permissible  for  non-cutting  of 
the  banks. 


88  ALIGNMENT,   SLOPE,  AND   CROSS-SECTION. 

In  the  light,  sandy  loam  soils  of  the  San  Luis  valley  in  Col- 
orado a  slope  of  6  inches  to  the  mile  given  on  the  Citizens' 
canal  has  proven  very  satisfactory.  So  low  a  slope  as  this  is 
possible,  because  the  water  is  comparatively  free  of  silt  and 
there  is  little  chance  of  its  deposition,  while  the  temperature  is 
so  low  that  there  is  little  likelihood  of  the  growth  of  weeds 
affecting  the  canal  bed.  In  the  gravelly  clays  through  which 
the  Turlock  canal  runs  a  satisfactory  grade  has  been  found  to 
be  1.5  feet  per  mile,  though  the  grade  is  changed  on  portions  of 
this  canal  according  to  the  character  of  the  soil,  until  in  the  cut 
through  loose  shale  near  the  canal  head  a  grade  of  7.9  feet  per 
mile  is  given,  producing  a  velocity  of  7^  feet  per  second  with 
satisfaction.  On  the  main  line  of  the  canal,  the  bed  width  of 
which  is  70  feet  and  depth  of  water  7^  feet  and  the  soil  a  light 
alluvial  loam,  the  grade  adopted  is  one  foot  per  mile.  Perhaps 
the  highest  grade  on  any  canal  is  that  on  a  short  portion  of 
the  Del  Norte  canal  in  Colorado,  where  the  fall  is  35  feet  per 
mile  through  a  rock  cut.  On  several  miles  of  this  canal  the 
grade  is  8  feet  per  mile,  but  after  it  reaches  the  earth  soil  in 
the  valley  it  is  reduced  to  1.2112. 

117.  Cross-sections. — The  most  economical  channel  is 
one  with  vertical  sides  and  a  depth  equal  to  half  the  bottom 
width,  but  this  form  is  only  applicable  to  the  firmest  rock. 
The  best  trapezoidal  form  is  one  in  which  the  width  of  the 
water  surface  is  double  the  bottom  width  and  equal  to  the 
sum  of  the  side  slopes.  Such  a  cross-section  as  this,  however, 
would  call  for  an  unusually  compact  material.  In  the  interest 
of  economy  the  side-slopes  above  water-level  should  be  as 
steep  as  the  nature  of  the  soil  will  permit.  As  before  shown, 
the  cross-sectional  area  depends  on  the  velocity  and  slope  and 
their  relation  to  the  quantity  of  water  to  be  discharged.  The 
exact  form  of  this  cross-section  is  dependent  on  the  topography 
and  the  material  through  which  the  canal  passes.  The  greater 
the  depth  the  greater  will  be  the  velocity  and  consequent  dis- 
charge for  the  same  form  of  cross-section. 

Very  large  canals,  such  as  some  of  those  in  India,  have  been 
given  a  proportion  of  depth  to  width  similar  to  that  of  the 


FORM   OF   CROSS-SECTION.  89 

great  rivers.  This  proportion  has  been  found  to  be  most 
nearly  attained  when  the  bed  width  is  made  from  13  to  16 
times  the  depth.  In  sidehill  excavation  the  greater  the  propor- 
tion of  depth  to  width  the  less  will  be  the  cost  of  construction 
(Art.  108.),  and  in  all  rock  and  heavy  material  it  is  desirable  if 
possible  to  make  the  bottom  width  not  greater  than  from  2  to  3 
times  the  depth.  Such  a  proportion  as  this,  however,  is  rarely 
practicable.  In  a  large  canal,  one  for  instance  having  a  capac- 
ity of  2000  second-feet,  with  a  velocity  of  2  feet  per  second, 
the  cross-sectional  area  should  be  1000  square  feet.  If  the 
proportion  of  2  to  I  were  maintained,  this  would  call  for  a 
bed  width  of  about  45  feet  to  a  depth  of  22\  feet.  Such  a 
depth  as  this  unless  in  very  hard  material,  is  readily  seen  to  be 
absurd,  as  the  cost  of  construction  would  be  greatly  increased 
over  that  of  a  canal  having  a  lesser  depth.  In  this  case  a  fair 
proportion  would  be  125  feet  bed  width  to  about  8  feet  depth. 
A  rule  which  has  been  proposed  and  which  will  prove  fairly 
good  on  moderate  sized  canals,  is  to  make  the  bottom  width  in 
feet  equal  to  the  depth  in  feet  plus  one,  squared.  This,  how- 
ever, will  not  apply  to  large  canals  and  is  not  altogether  true 
for  any  size  of  canal. 

118.  Form  of  Cross-section. — The  cross-section  of  a 
canal  may  be  so  designed  that  the  water  may  be  wholly  in 
excavation,  wholly  in  embankment,  or  partly  in  excavation 
and  partly  in  embankment  (Fig.  12).  The  conditions  which 
govern  the  choice  of  one  of  these  three  forms  are  dependent 
primarily  on  the  alignment  and  grade  of  the  canal,  and  second- 
arily on  the  character  of  the  soil.  For  sanitary  reasons  it  is 
sometimes  desirable  to  keep  a  canal  wholly  in  cutting,  for  if 
the  material  of  which  the  banks  are  constructed  is  porous  the 
water  may  filter  through  and  stand  about  in  stagnant  pools  on 
the  surface  of  the  ground.  If  the  material  is  impervious  to 
the  passage  of  water  and  will  form  good  firm  banks,  it  may 
be  well  to  keep  the  canal  in  embankment  where  possible, 
though  this  may  necessitate  the  expense  of  borrowing  material. 
In  order  to  lessen  the  cost  of  construction,  it  is  desirable,  where 
the  surface  will  permit,  to  keep  a  canal  half  in  cut  and  half  in 


90  ALIGNMENT,   SLOPE,  AND    CROSS-SECTION. 

fill,  thus  reducing  to  a  minimum  the  amount  of  material  to  be 
moved.  Ordinarily  the  surface  of  the  ground  is  irregular  and 
undulating,  and  in  order  that  the  grade  may  be  maintained 
the  canal  will  of  necessity  be  sometimes  wholly  in  cut  and  at 
others  wholly  in  fill,  and  at  others  at  all  intermediate  stages 
between  these.  Where  the  canal  is  wholly  in  embankment 
there  is  always  considerable  loss  from  leakage,  and  consequent 


WITHOUT   BERMS  —  W.L.  BELOW  C.L 


SIDELONG  GROUND  .W.L./XBOVE  C.L. 


FIG.  12.— VARIOUS  CANAL  CROSS-SECTIONS. 


danger  of  breaches.  Where  the  canal  is  wholly  in  cut,  care 
must  be  taken  to  discover  the  character  of  the  soil  in  which 
the  excavation  is  to  be  made,  as  rock  may  be  encountered  at 
a  few  inches  below  the  surface,  thus  increasing  the  cost  of 
excavation,  or  a  sandy  substratum  may  be  discovered  which 
would  cause  excessive  seepage. 

Most  main  canals  follow  the  slope  of  the  country  on  grade 
contours  running  around  sidehill  or  mountain  slopes.  In 
such  cases  it  is  necessary  to  build  an  embankment  on  one  side 
only,  when  the  cutting  will  be  entirely  on  the  upper  side.  If 
there  is -a  gentle  slope  on  the  upper  side,  and  consequently  an 
embankment  on  that  side,  it  is  desirable  to  run  drainage  chan- 
nels at  intervals  from  this  embankment  to  keep  the  water  from 
making  its  way  thro.ugh  it  to  the  canal.  These  drainage  chan- 


SIDE   SLOPES  AND    TOP    WIDTH   OF  BANKS.  9 1 

nels  may  be  taken  through  the  embankment  into  the  canal, 
or  may  be  led  away  to  some  natural  watercourse. 

In  designing  the  cross-section  of  a  canal  it  maybe  desirable 
to  give  a  berm,  and  this  may  be  above  or  below  the  water- 
level  (Fig.  12).  Ordinarily  the  berm  is  left  at  a  level  with  the 
ground  surface,  though  it  may  be  constructed  in  excavation  or 
embankrnent, — an  unusual  practice,  however.  The  chief  object 
of  the  berm  is  to  provide  against  the  destruction  of  the  slopes 
in  the  lower  part  of  the  banks  by  giving  a  terrace  or  bench  on 
which  the  upper  bank  may  slide,  providing  it  fails  to  maintain 
the  slope  originally  given  ;  it  also  serves  in  some  cases  as  a 
tow-path  or  foot-path.  The  width  of  berm  varies  between  2 
and  6  feet,  and  it  is  common  to  change  the  slopes  at  the  point 
of  junction  between  cut  and  embankment,  making  the  slope 
of  the  latter  a  little  flatter  than  that  of  the  former. 

119.  Side  Slopes  and  Top  Width  of  Banks. — In  large 
canals  it  is  always  desirable  to  have  a  roadbed  on  at  least  one 
bank,  and  the  width  of  this  will  determine  the  top  width  of  the 
bank.  The  inner  surfaces  of  the  canal  are  usually  made 
smooth  and  even,  while  the  top  is  likewise  made  smooth,  with 
a  slight  inclination  to  the  outward  to  throw  drainage  away 
from  the  canal.  The  inner  slopes  of  the  banks  vary  in  soil 
from  i  on  i  to  i  on  4,  according  to  the  character  of  the  mate- 
rial. In  firm  clayey  gravel  or  hardpan  slopes  of  i  on  i  are 
sufficiently  substantial  for  nearly  any  depth  of  cutting  or 
embankment.  On  the  Turlock  canal  in  California  is  a  cut  80 
feet  in  depth  with  side  slopes  of  I  on  i,  while  on  the  Bear 
river  canal  in  Utah  are  similar  slopes  in  disintegrated  shale 
in  coarse  gravel.  In  ordinary  firm  soil  mixed  with  gravel  or 
coarse  loamy  gravel  slopes  of  i  on  I  j-  are  sufficient.  In  firm 
soil  and  slightly  clayey  loam  slopes  of  I  on  2  may  be  required  ; 
on  lighter  soils  these  slopes  may  be  increased  until  the  lightest 
sand  is  reached,  when  slopes  of  i  on  4  may  be  necessary. 

The  top  width  of  the  canal  bank  is  generally  from.  4  to  10 
feet,  according  to  the  material,  depth,  and  whether  or  not  the 
water  is  in  embankment.  If  there  is  to  be  no  roadway  on  the 
top  of  the  embankment,  and  the  surface  of  the  water  does  not 


92  ALIGNMENT,   SLOPE,  AND    CROSS-SECTION. 

rise  more  than  a  foot  or  so  above  the  foot  of  the  embankment, 
a  top  width  of  4  feet  is  sufficient.  Where  the  depth  of  water 
on  the  embankment  is  greater,  this  width  should  be  6  or  8 
feet,  and  if  the  soil  is  light  it  should  be  at  least  10  feet.  It  is 
sometimes  necessary  to  build  a  puddle  wall  in  the  embank- 
ment, or  to  make  a  puddle  facing  on  its  inner  slope  where  it  is 
particularly  pervious  to  water.  The  same  effect  is  obtained  by 
sodding  or  causing  grass  to  grow  on  the  bank.  It  may  be 
well  to  puddle  the  entire  bank  during  construction  by  laying 
and  rolling  it  in  layers.  The  carrying  capacity  of  a  canal 
should  be  so  calculated  that  the  surface  of  the  water  when  in 
cut  shall  not  reach  within  one  foot  of  the  top  of  the  ground 
surface.  In  fill  the  depth  of  water  carried  should  be  such  that 
the  surface  shall  not  rise  higher  than  within  \\  feet  of  the  top 
of  the  bank,  while  if  the  fill  is  great  it  is  often  unsafe  to  let 
the  water  rise  within  2  feet  of  the  top  of  the  bank. 

120.  Cross-section  with  Subgrade. — In  the  light  soils 
of  the  San  Luis  valley  in  Colorado  and  in  Kern  valley  in  Cali- 
fornia it  has  been  found  advantageous  to  use  a  different  form 
of  cross-section  than  that  above  described.  Experience  in  the 
regions  above  cited  has  shown  that  the  subgrade  produces  a 
form  approaching  that  of  the  ellipse.  This  cross-section  tends 
to  keep  the  current  in  the  centre  of  the  channel,  and  to  keep 
up  its  flow  with  the  least  exposure  to  friction  and  seepage 
when  the  volume  of  water  in  the  canal  is  low.  The  sub- 
grade  (Fig.  13)  is  given  by  practically  designing  the  canal  as 


FIG.  13.— CROSS-SECTION  OF  GALLOWAY  CANAL  SHOWING  SUBGRADB. 

if  it  were  to  have  a  trapezoidal  cross-section  with  berm,  and 
then  evening  off  the  slope  by  removing  the  berm  and  continu- 
ing the  slope  from  the  bottom  of  the  canal  toward  the  centre 
to  a  depth  or  subgrade  of  from  I  to  2  feet  below  the  original 
bed  of  the  canal.  In  such  construction  as  this  it  has  some- 
times been  found  desirable  to  give  the  bank  practically  no  top 


CXOSS-SECTION  IN  ROCK. 


93 


width,  simply  rounding  it  off  from  the  inner  to  the  outer  sur- 
face, where  the  waste  is  carelessly  scattered,  allowing  the  soil 
to  assume  its  natural  slope. 

121.  Shrinkage  of  Earthwork. — It   is  well  known  that 
when  -soil  which  has  been  removed   from    an  excavation    is 
formed  into  embankment  it  settles  or  shrinks  in  volume.    That 
is  to   say,  the  excavated  and  embankment  soil  occupies  a  less 
space  than  it  did  in  the  ground ;    while,  on  the  contrary,  rock 
or  loose   stone  occupies  a  greater  space,  depending  on  the 
dimensions  of  the  fragments.    The  percentage  of  this  shrinkage 
differs  according  to  different  soils.     The  following  list  gives  an 
idea  of  the  amount  of  this  shrinkage  for  different  soils : 

Sand,  about  10  per  cent ;  in  other  words,  after  excavation 
sand  will  ultimately  occupy  10  per  cent  less  space  than  it  did 
in  its  natural  bed. 

Sand  and  gravel  shrink  8  per  cent. 

Earth,  loam,  and  sandy  loam  shrink  10  to  12  per  cent. 

Gravelly  clay  shrinks  8  to  10  per  cent. 

Puddled  clay  and  puddled  soil  shrink  20  to  25  per  cent. 

Rock  expands  or  increases  in  volume  from  25  per  cent  in 
the  case  of  small  or  medium  fragments  and  road-metalling  to 
60  or  70  per  cent  in  large  fragments  carelessly  thrown. 

122.  Cross-section  in  Rock. — In  firm  rock  it  is  desirable 
to  make  the  proportion  of  depth  to  width  about  as  i   to  2, 


FIG.  14.— ROCK  CROSS-SECTION.    TURLOCK  CANAL. 

with  side  slopes  of  about  4  on    I.     In  less  firm  rock  lighter 
slopes  and  a  less  proportional  depth  are  desirable.     In  friable 


94 


ALIGNMENT,   SLOPE,  AND    CROSS-SECTION. 


shale,  as  on  the  Turlock  canal  in  California,  a  different  cross- 
section  is  desirable  (Fig.  14).  In  this  instance  a  retaining-wall 
of  hand-placed  stones,  with  an  outer  slope  of  4  on  I  and  a  top 
width  of  2,\  feet,  is  built  on  the  lower  side.  Inside  this  is  a 
puddled  earth  bank,  riprapped  on  the  water  surface  with  10 
inches  in  thickness  of  loose  stone.  The  upper  or  excavated 
slope  is  about  2  on  i,  the  depth  10  feet,  and  the  bed  width 
20  feet.  On  the  Bear  River  canal  in  Utah,  the  cross-section 


W/M 

FIG.  15.— ROCK  CROSS-SECTION,  BEAR  RIVER  CANAL. 

shown  in  Fig.  1 5  was  given  in  order  to  avoid  too  much  exca- 
vation in  extremely  rocky  sidehill. 


>          CHAPTER   XII. 
HEADWORKS  AND  DIVERSION  WEIRS. 

123.  Location  of  Headworks.— The  headworks  of  a  canal 
are  generally  placed  where  the  stream  emerges  from  the  hills. 
At  such  a  point  the  slope  of  the  country  and  of  the  stream  is 
steep,  making  it  possible  to  conduct  a  canal  thence  to  the 
irrigable  lands  with  the  shortest  diversion  line.  Moreover,  the 
width  of  the  channel  of  the  stream  is  generally  contracted, 
and  it  flows  through  firm  soil  or  rock,  thus  permitting  a  reduc- 
tion in  the  length  of  the  weir  and  in  the  cost  and  character  of 
its  construction. 

When  the  volume  of  flood  water  occurring  in  the  stream  is 
great  it  is  sometimes  necessary  to  locate  the  headworks  at  a 
point  where  the  width  between  banks  is  greatest,  in  order  that 
the  depth  of  water  flowing  over  the  weir  may  be  reduced  to 
a  minimum  and  danger  of  its  destruction  reduced  accord- 
ingly. While  such  a  location  may  be  the  most  permanent,  it 
is  also  most  costly  for  construction.  The  site  of  the  headworks 
should  be  such  that  the  most  permanent  weir  can  be  con- 
structed at  the  least  cost,  and  yet  they  should  be  so  located 
that  the  diverting  canal  can  be  conducted  thence  to  the  irri- 
gable lands  at  a  minimum  cost.  The  location  of  the  head- 
works  high  up  on  the  stream  is  usually  antagonistic  to  the  last 
object,  since  it  generally  results  in  the  canal  having  to  en- 
counter heavy  rock  work  and  difficult  construction  until  it  gets 
away  from  the  river  banks. 

95 


96  HEADWORKS  AND  DIVERSION    WEIRS. 

124.  Character  of  Headworks. —  The  headworks  of  a 
canal  consist — 

1.  Of  the  diversion  weir,  in  which  is  usually  built : 

2.  A  set  of  scouring  sluices  ; 

3.  Of  a  regulator  at  the  head  of  the  canal  for  its  control  ; 

4.  Of  an  escape  for  the  relief  of  the  canal  below  that  point. 
Sometimes  to  these  are  added  river  training  or  regulating 

works  for  the  .protection  of  the  banks  of  the  stream  above 
and  below  the  obstruction  formed  by  the  >headworks.  Too 
careful  attention  cannot  be  given  to  an  examination  of  the 
stream  at  the  point  of  diversion.  Soundings  and  borings 
should  be  made  to  ascertain  the  depth  of  water  and  character 
of  the  foundation.  The  velocity  of  the  stream  and  its  flood 
heights  should  be  studied,  as  should  the  material  of  which  the 
banks  are  composed.  Where  possible,  a  straight  reach  in  the 
river  should  be  chosen  for  the  location  of  the  headworks  in 
order  that  the  stream  shall  have  a  direct  sweep  past  them, 
thus  reducing  to  a  minimum  the  deposition  of  silt  in  front  of 
the  regulating  gates.  If  possible,  a  point  should  also  be  chosen 
where  the  velocity  in  the  river  will  not  exceed  that  in  the 
canal,  so  that  the  deposition  of  silt  shall  be  further  reduced. 

There  has  been  too  great  a  tendency  in  American  construc- 
tion to  build  works  of  a  temporary  and  transient  character. 
The  headworks  of  a  canal  are  the  most  vital  portions  of  its 
mechanism  ;  they  are  to  a  canal  system  what  a  throttle-valve  is 
to  a  locomotive.  Through  them  the  permanency  of  the  supply 
in  the  canal  is  maintained,  and  any  injury  to  them  means 
paralysis  to  the  entire  system.  They  should  therefore  he 
most  substantially  and  carefully  designed  throughout.  The 
employment  of  wood  is  altogether  too  common  in  the  United 
States.  It  is  very  well  to  make  use  of  wood  as  a  temporary 
makeshift  until  money  and  time  can  be  found  for  substituting 
more  substantial  material.  It  may  be  generally  laid  down 
as  a  principle,  however,  that  only  iron  and  masonry  should 
enter  into  the  construction  of  the  headworks.  It  is  impossible 
to  form  wood,  with  the  addition  of  little  or  no  iron  or  masonry, 
into  permanent  and  substantial  headworks.  The  best  and 


DIVERSION    WEIRS.  97 

most  abundant  examples  of  substantial  headworks  must  still 
be  sought  in  Europe  and  India. 

In  some  cases  it  has  been  found  unnecessary  to  construct 
diversion  weirs  as  a  part  of  the  headworks  of  a  canal.  This 
has  been  the  case  especially  where  the  discharge  of  the 
stream  was  great  relative  to  the  discharge  of  the  canal,  and 
only  when  a  portion  of  the  water  in  the  stream  was  re- 
quired. Thus,  on  the  Central  Irrigation  District  canal  in  Cali- 
fornia no  diversion  weir  is  required.  The  canal  heads  in  a 
simple  cut,  its  bed  being  a  few  feet  below  the  lowest  water- 
level  in  the  Sacramento  river.  At  the  head  of  the  Ganges 
and  Jumna  canals  in  India  there  are  no  permanent  diversion 
works,  the  water  being  turned  into  the  canal  head  by  means 
of  temporary  structures  of  bowlders,  or  by  means  of  training 
the  water  of  the  river  so  that  it  shall  flow  directly  against  the 
canal  head. 

125.  Diversion  Weirs. — In  this  book  the  word  weir  as 
distinguished  from  dam  is  generally  employed  to  mean  a 
structure  intended  either  for  the  impounding  or  diversion  of 
water  and  over  which  flood  waters  may  safely  flow.  Thus  weirs 
are  usually  built  at  the  heads  of  canals  for  the  diversion  of  the 
waters  of  the  streams  into  their  heads,  while  the  surplus  water 
is  permitted  to  flow  over  the  weir  and  to  pass  on  down  the 
stream.  In  some  cases,  however,  dams  over  which  it  would  be 
unsafe  to  permit  flood  waters  to  pass  are  used  for  the  purpose 
of  diversion,  and  a  wasteway  is  constructed  at  one  end  of  the 
dam  for  the  passage  of  surplus  waters. 

A  weir  across  a  stream  is  analogous  to  a  bar  and  should  be 
located  and  treated  as  such.  If  it  is  placed  at  the  widest 
part  of  the  stream  the  cost  of  construction  may  be  increased. 
In  the  great  rivers  of  India  where  diversion  is  made  in  the 
level  and  sandy  plains  below  the  hills  and  where  permanent 
foundations  cannot  be  obtained,  weirs  have  generally  been 
placed  in  the  broadest  reaches  of  the  streams.  This  is  the 
case  at  Okhla  at  the  head  of  the  Agra  canal,  and  at  Narora  at 
the  head  of  the  Lower  Ganges  canal.  In  our  own  country 
diversion  for  canals  has  generally  taken  place  in  the  foothills, 


98  HEADWORKS  AND  DIVERSION    WEIRS. 

and  accordingly  the  narrower  portions  of  the  streams   have 
been  chosen  for  this  purpose. 

126.  Classes  of  Weirs. — Weirs  may  be  divided  into  two 
classes  according  to  the   mode  of  building  their   foundations. 
Thus  they  may  rest  directly  on  some  permanent  material ;  or 
they  may  rest  on  some  unstable  material,  as  quicksand,  gravel, 
or  clay,  in  which  case  an  artificial  foundation  of  piles,  caissons, 
or  wells   or   blocks   must  be  constructed.     Where,  in  western 
practice,  a  firm  foundation  has  not  been  found  piling  has  usu- 
ally been  employed.     In  India  and  Egypt  wells  or  blocks  are 
employed  for  foundations  in  unstable  material. 

These  consist  of  rectangular  boxes  or  cylinders  of  brick, 
which  rest  on  a  sharp  cutting  edge,  and  from  the  interior  of 
which  the  earth  is  excavated  as  the  well  sinks.  After  it  has 
reached  a  suitable  depth  it  is  filled  in  with  concrete,  the  whole 
depending  for  its  stability  chiefly  on  the  friction  of  its  sides 
against  the  surrounding  material. 

The  most  convenient  classification  of  diversion  weirs  is 
according  to  the  construction  of  their  superstructures.  These 
may  be — 

1.  Temporary  brush  or  bowlder  barriers  ; 

2.  Rectangular  walls  of  sheet  and  anchor  piles  filled  with 
rock  or  sand  ; 

3.  Open  weirs ; 

4.  Wooden  crib  and  rock  weirs ; 

5.  Masonry  weirs. 

127.  Brush  and    Bowlder  Weirs.— The    simplest     and 
crudest  form  of  weir  is  the  brush  and  gravel  barrier,  which  was 
originally  used  by  the  Mexicans  and  is  still  employed  in  the 
West  on  minor  streams.     These  weirs  are  formed  by  driving 
stakes  across  the   channel  and  attaching  to  them  fascines  or 
bundles  of  willows  from  three  to  six  inches  in  diameter  at  the 
butts,  which  are  laid  with  the  brush  end    up-stream,  and  are 
weighted  with  bowlders  and  gravel.     More  willow  or  cotton- 
wood  branches  are  laid  on  the  top  of  these  and  again  weighted 
with  bowlders,  this  operation  being  continued  until  the  struc- 
ture is  built  to  a  height  of  three  or  four  feet.     Such  structures 


OPEN  AND    CLOSED    WEIRS.  99 

are  of  the  crudest  character  and  can  be  built  without  any  en- 
gineering knowledge  or  supervision. 

128.  Rectangular   Pile   Weirs. — These    have    been    em- 
ployed   in    wide   sandy   rivers   like    the    Platte,    in    Colorado. 
They  consist  of  a  double  row  of  piling  driven  into  the  river 
bed,  the  two   rows   being  about  6  feet   apart,  and   the  piles 
about  3  feet  apart  between  centres.     Between  these  is  driven 
sheet  piling  to  prevent  the  seepage  or  travel  of  water  through 
the  barrier,  and  the  upper  portion  of  the  structure  is  planked 
so  as  to  form  a  rectangular  wall  the  interior  of  which  is  filled 
in  with  gravel,  sand,  etc.     Such  walls,  are  usually  low,  rarely 
exceeding  8  feet  in  height,  and  after  the  upper  side  is  backed 
with  the  silt  deposited  from  the  stream  they  form  substantial 
barriers  which    may   last    for   many   years.      Such   structures 
cannot  be  employed  where  the  flood  height  is  great,  as  they 
would   soon    be    undermined    unless   substantial   aprons  were 
constructed. 

129.  Open   and   Closed   Weirs. — Diversion    weirs    may 
again  be  classified  as  open  or  closed.     A  closed  weir  is  one  in 
which   the   barrier  which   it  forms   is  solid   across   nearly  the 
entire  width  of  the  channel,  the  flood  waters  passing  over  its 
crest.     Such  weirs  have  usually  a  short  open  portion  in  front 
of  the  regulator  known  as  the  "  scouring  sluice,"  the  object  of 
which  is  to  maintain  a  swift  current  past  the  regulator  entrance, 
and  thus  prevent  the  deposit  of  silt   at  that  point.     An  open 
weir  is  one  in  which  scouring  sluices  or  openings  are  provided 
throughout  its  entire  length. 

The  advantage  of  the  closed  weir  is  that  it  is  self-acting, 
and  if  well  designed  and  constructed  requires  little  expense 
for  repairs  or  maintenance.  It  is  a  substantial  structure,  well 
able  to  withstand  the  shocks  of  floating  timber  and  drift ;  but 
it  interferes  with  the  normal  regimen  of  the  river,  causing 
deposit  of  silt  and  perhaps  changing  the  channel  of  the 
stream.  Open  or  scouring  sluice  weirs  interfere  little  with 
the  normal  action  of  the  stream,  and  the  scour  produced  by 
opening  the  gates  prevents  the  deposit  of  silt,  while  their  first 
cost  is  generally  less  than  that  of  closed  weirs. 


100  HEADWORKS  AND  DIVERSION    WEIRS, 

The  closed  weir  consists  of  an  apron  properly  founded  and 
carried  across  the  entire  width  of  the  river  flush  with  the  level 
of  its  bed,  and  protected  from  erosive  action  by  curtain-walls 
up  and  down  stream.  On  a  portion  of  this  is  constructed  the 
superstructure,  which  may  consist  of  a  solid  wall  or  in  part  of 
upright  piers,  the  interstices  between  which  are  closed  by 
some  temporary  arrangement.  This  portion  of  the  weir  is 
called  the  scouring  sluice.  The  apron  of  the  weir  should 
have  a  thickness  equal  to  one  half  and  a  breadth  equal  to 
three  times  the  height  of  the  weir  above  the  stream  bed. 
During  floods  the  water  backed  against  the  weir  acts  as  a 
water  cushion  to  protect  the  apron,  and  as  the  flood  rises  the 
height  of  the  fall  over  the  weir  crest  diminishes,  so  that  with  a 
flood  of  16  feet  over  an  ordinary  weir  its  effect  as  an  obstruc- 
tion wholly  disappears. 

An  open  weir  consists  of  a  series  of  piers  of  wood,  iron  or 
masonry,  set  at  regular  intervals  across  the  stream  bed  and 
resting  on  a  masonry  or  wooden  floor.  This  floor  is  carried 
across  the  channel  flush  with  the  river  bed,  and  is  protected 
from  erosive  action  by  curtain-walls  up  and  down  stream. 
The  piers  are  grooved  for  the  reception  of  flashboards  or 
gates,  so  that  by  raising  or  lowering  these  the  afflux  height  of 
the  river  can  be  controlled.  The  distance  between  the  piers 
varies  between  3  and  10  feet,  according  to  the  style  of  gate 
used.  If  the  river  is  subject  to  sudden  floods  these  gates 
may  be  so  constructed  as  to  drop  automatically  when  the 
water  rises  to  a  sufficient  height  to  top  them.  It  is  sometimes 
necessary  to  construct  open  weirs  in  such  manner  that  they 
shall  offer  the  least  obstruction  to  the  waterway  of  the  stream. 
This  is  necessary  in  weirs  like  the  Barage  du  Nil  below  Cairo, 
Egypt,  or  in  some  of  the  weirs  on  the  Seine,  in  France,  in 
order  that  in  time  of  flood  the  height  of  water  may  not 
be  appreciably  increased  above  the  fixed  diversion  height. 
Should  the  height  be  increased  in  such  cases  the  water  would 
back  up,  flooding  and  destroying  valuable  property  in  the  cities 
above.  Under  such  circumstances  open  weirs  are  sometimes 
so  constructed  that  they  can  be  entirely  removed,  piers  and  all, 


OPEN  FRAME   OR   FLASHBOARD    WEIRS.  IOI 

leaving  absolutely  no  obstruction  to  the  channel  of  the  stream, 
and  in  fact  increasing  its  discharging  capacity,  owing  to  the 
smoothness  which  they  give  to  its  bed  and  banks. 

130.  Open  Frame  or  Flashboard  Weirs. — A  form  of 
cheap  open  weir  which  has  been  commonly  constructed  in  the 
West  is  the  open  wooden  frame  and  flashboard  weir.  This 
type  of  structure  is  used  only  on  such  rivers  as  have  unstable 
beds  and  banks,  where  any  obstruction  to  the  ordinary  regimen 
of  the  stream  would  cause  a  change  in  its  channel.  It  con- 
sists wholly  or  in  part  of  a  foundation  of  piling  driven  into  the 
river  bed,  upon  which  is  built  an  open  framework  closed  by 
horizontal  planks  let  into  slots  in  the  piers.  These  weirs  are 
constructed  of  wood,  and  are  temporary  in  character,  their 
chief  recommendation  being  the  cheapness  with  which  they 
can  be  built  in  rivers  the  beds  of  which  are  composed  of  a 
considerable  depth  of  silt  or  light  soil. 

Two  varieties  of  this  weir  are  in  common  use.  One 
(Fig.  16),  which  has  been  employed  at  the  heads  of  the  Del 


FIG.  16.— OPEN  WEIR.    MONTE  VISTA  CANAL. 

Norte,  Monte  Vista  and  other  canals  in  the  San  Luis  valley 
of  Colorado,  is  partly  open  and  partly  closed.  An  earth  bank 
or  dam  is  built  for  a  portion  of  the  way  across  the  stream  and 
of  such  height  that  it  will  not  be  topped  by  floods.  The 
remainder  of  the  weir  consists  of  a  framework  of  rough- 
hewn  logs  founded  on  piles,  the  abutments  of  which  are  pro- 
tected by  wooden  planking  built  against  the  earthen  dam. 
The  openings  between  the  frames  or  piers  are  about  6  feet 
apart,  and  the  crest  of  the  weir  rarely  exceeds  5  feet  in  height 
above  the  normal  water  surface.  Between  the  piers  horizontal 
planks  or  flashboards  can  be  inserted  one  at  a  time,  thus 


IO2 


HEADWORDS  AND   DIVERSION    WEIRS. 


OPEN  FRAME    OR  FLASHBOARD    WEIRS. 


103 


closing  the  waterway  to  any  desired  extent  up  to  the  level  of 
the  weir  crest. 

A  more  common  and  finished  type  of  frame  or  flashboard 
weir  is  that  employed  on  the  Kern  river  in  California,  at  the 
heads  of  the  canals  in  that  neighborhood.  An  example  of  these 
is  the  weir  at  the  head  of  the  Galloway  canal  (Fig.  17),  which 
consists  of  100  bays,  each  separated  by  a  simple  open  tri- 
angular framework  of  wood  founded  on  piles,  the  width  of 


FIG.  17. — CROSS-SECTION  OF  OPEN  WEIR,  GALLOWAY  CANAL. 

each,  opening  or  bay  being  4  feet.  In  constructing  this  weir 
the  area  to  be  built  upon  was  inclosed  in  sheet  piling  and 
covered  with  a  floor  placed  2^  feet  below  the  bed  of  the 
stream.  Above  this  floor  is  a  second  floor,  about  2  feet  in 
height,  the  walls  forming  compartments  which  are  filled  with 
sand,  thus  making  a  sand  box  apron,  on  which  the  waters  fall. 
This  apron  is  carried  up  and  down  stream  for  a  distance  of 
about  10  feet  in  each  direction.  The  weir  proper  is  formed  of 
frames  or  trusses  of  6  by  6  inch  timber,  placed  transversely 


IO4  HEADWORKS  AND   DIVERSION    WEIRS. 

NARORA    WEIR-LOWER    GANGES   CANAL 
length  1260  metres 

H.F.I 


ofStver 


OKHLA   WEIR-AGRA    CANAL. 
743  metres 

H.r,L 


DEHREE   WEJR-SOANE  CANAL 

length  d825  metres 


-JET" 


BEZWARA     WEIR  -  KISTNA  CANAL. 
length  1150  metres. 


1{ 

I 


60DIVERY        WEIR. 
length  6274  metres. 


PLATE  III. — CROSS-SECTIONS  OF  INDIAN  WEIR 


OPEN  MASONRY    WEIRS,  INDIAN   TYPE.  IO5 

4  feet  apart.  These  frames  consist  of  2  pieces,  the  up-stream 
piece  being  7  feet  2  inches  long  and  set  at  an  angle  of  38  degrees, 
while  the  other  supports  it  at  right  angles  and  is  5  feet  4 
inches  long.  The  lower  ends  of  these  rafters  thrust  against 
two  pieces  of  6  by  2  inch  timber  running  the  whole  length  of 
the  weir  and  nailed  to  the  flooring.  These  frames  are  sup- 
ported directly  on  anchor  piles,  one  at  each  end  joiced  into 
the  framing.  These  trusses  are  kept  in  vertical  position  by 
means  of  a  footboard  running  transversely  the  entire  width  of 
the  stream..  On  the  up-stream  face  of  the  trusses  planks  or 
flashboards  which  slide  between  grooves  formed  by  nailing 
face-boards  on  the  trusses  are  laid  on  to  the  required  height. 
This  weir  is  10  feet  in  height  above  the  wooden  floor,  which  is 
flush  with  the  river  bed. 

131.  Open  Masonry  Weirs,  Indian  Type. — A  substantial 
form  of  open  masonry  weir  is  that  generally  constructed  on 
Indian  rivers,  where  the  banks  and  bed  are  of  sand,  gravel,  or 
other  unstable  material.  These  weirs  generally  rest  on  shallow 
foundations  of  masonry,  in  such  manner  that  they  practically 
float  on  the  sandy  beds  of  the  streams.  The  foundation  of  such 
a  weir  is  generally  of  one  or  more  rows  of  wells  sunk  to  a 
depth  of  from  6  to  10  feet  in  the  bed  of  the  river,  the  wells  and 
the  spaces  between  the  rows  of  wells  being  filled  in  with  con- 
crete, thus  forming  a  masonry  wall  across  the  channel.  This 
form  of  construction  is  illustrated  in  PL  III,  which  exhibits 
several  different  types  of  such  works.  The  weir  at  the  head 
of  the  Soane  canals,  which  is  typical  of  this  class  of  structure, 
consists  of  three  parallel  lines  of  masonry  running  across  the 
entire  widtrijthe  stream,  and  varying  from  2^-  to  5  feet  in  thick- 
ness. The  main  wall,  which  is  the  \ipper  of  the  three  and  the 
axis  of  the  weir,  is  5  feet  wide  and  8  feet  high,  and  all  three 
lines  of  walls  are  founded  on  wells  sunk  from  6  to  8  feet  in 
the  sandy  bed  of  the  river.  Between  these  walls  is  a  simple 
dry  stone  packing  raised  to  a  level  with  their  crests,  thus  form- 
ing an  even  upper  surface.  The  up-stream  slope  is  I  on  3,  and 
the  down-stream  slope  i  on  12,  the  total  length  of  this  lower 


io6 


HEADWORKS  AND  DIVERSION    WEIRS. 


slope  being  104  feet,  while  the  total  height  of  the  weir  includ- 
ing its  foundation  is  19.3  feet. 

The  Soane  weir  has  a  total  length  across  stream  of  12,480 
feet,  of  which  1494  feet  consists  of  open  weir  disposed  in  three 
sets  of  scouring  sluices  (Fig.  18),  one  in  the  centre  and  two 


Elevation. 


\Z  470' 


Cross  Section  of  Weir . 

3o'       *4>t —  70'  -» 


FIG.  18.— HALF  ELEVATION  AND  PLAN,  AND  SECTION  OF  SOANE  WEIR,  INDIA. 

adjacent  to  either  bank  and  in  front  of  the  regulating  gates  at 
the  head  of  the  canals.  These  scouring  sluices  consist  of  three 
parts, — the  foundation,  the  floorway  or  apron,  and  the  super- 
structure. The  floor  is  deep  and  well  constructed  of  substan- 
tial masonry,  and  is  continued  for  a  short  distance  above  the 
weir  and  for  a  considerable  distance  below  it.  It  is  90  feet 
wide  parallel  to  the  river  channel,  and  is  founded  on  wells,  the 


OPEN  MASONRY    WEIRS,   INDIAN    TYPE.  IO/ 

ashlar  pavement  of  the  floor  being  15  inches  thick  in  the 
bottom  of  the  scouring  sluices  between  the  piers,  and  9  inches 
thick  over  the  remainder  of  the  apron.  Up-stream  from  the 
sluice  floor  for  a  distance  of  25  feet  is  a  line  of  wells  sunk  to  a 
depth  of  10  feet  as  a  curtain-wall  to  the  apron.  Twenty-five 
feet  down-stream  from  the  flooring  of  the  sluices  is  a  similar 
line  of  wells  formed  into  a  wall,  and  the  spaces  between  these 
two  curtain-walls  and  the  main  ashlar  flooring  of  the  sluice- 
way is  packed  with  dry-laid  bowlders  and  rubble  covered 
with  a  pavement  of  masonry  9  inches  in  thickness.  Down- 
stream from  the  lower  curtain-wall  a  paving  of  large  bowl- 
ders stretches  for  50  feet  further,  the  whole  of  this  sluice 
floor  parallel  to  the  river  channel  being  200  feet  in  length. 
This  is  a  typical  floor  to  an  Indian  open  weir  or  sluiceway,  on 
top  of  which,  in  line  with  the  centre  of  the  crest  of  the  weir, 
are  built  up  masonry  piers  at  regular  intervals  of  from  6  to  12 
feet  apart,  grooved  for  the  reception  of  planks  or  flashboards, 
or  closed  with  lifting  or  automatic  drop-gates. 

A  peculiar  form  of  open  weir  is  that  constructed  at  the 
head  of  the  Sidhnai  canal  in  India.  At  the  point  where  the 
vveir  is  built  the  bed  of  the  river  gives  a  good  clay  foundation 
for  a  short  distance  from  either  bank,  while  in  the  centre  of 
the  channel  the  bed  is  of  sand  for  a  considerable  depth.  Sheet 
piling  10  feet  long  was  driven  into  the  sandy  bed  of  the  river 
to  prevent  excessive  percolation.  On  these  piles  (Fig.  19)  rests 
a  series  of  piers  which  support  masonry  arches,  the  piers  being 
16  feet  between  centres  and  filled  between  with  clay.  Above 
this  masonry  arch  is  built  a  continuous  wall  across  the  entire 
width  of  the  streem  from  4  to  6  feet  wide  on  top  and  from  3^- 
to  8|  feet  in  height.  Over  this  wall,  parallel  to  the  channel  of 
the  river,  is  built  a  masonry  flooring,  the  upper  slope  of  which 
is  I  on  3,  while  its  lower  slope  varies  between  I  on  5  and  I  on 
10,  according  as  it  is  near  the  centre  or  ends  of  the  weir.  The 
total  width  of  this  floor  parallel  to  the  channel  of  the  stream  is 
12  feet  above  the  axis  of  the  weir  and  40  feet  below  it,  the 
lower  toe  terminating  in  a  series  of  wells.  On  top  of  this 
flooring  are  erected  a  series  of  piers  23  feet  apart  between 


108 


HEADWORKS  AND   DIVERSION    WEIRS. 


centres,  and  projecting  2\  feet  up-stream  from  the  central  wall 
and  9  feet  down-stream,  their  total  length  parallel  to  the  channel 
being  1  5^  feet  and  their  width  on  top  6  feet.  The  crests  of 
these  pillars  are  6£  feet  in  height  above  the  crest  of  the  floor, 
while  the  total  height  of  the  weir  above  the  summit  of  the  pile 
foundation  is  about  21  feet.  It  will  thus  be  seen  that  this 
weir  offers  a  clear  waterway  across  the  entire  channel,  ob- 
structed only  by  the  piers,  which  are  6J  feet  above  the  stream- 
bed.  The  openings  between  these  piers  are  closed  by  means 


iiillljl 


FIG.  19.— ELEVATION  AND  CROSS-SECTION  OF  SIDHNAI  WEIR,  INDIA. 

of  needles,  which  consist  of  a  heavy  beam  laid  along  the  crest 
wall  from  pier  to  pier,  against  which  rest  wooden  sticks  or 
needles  inclined  at  a  slight  angle.  These  needles  are  each  /£ 
feet  long  by  5  inches  wide  and  3^  inches  in  thickness,  and  are 
laid  along  the  upper  face  close  together  so  as  to  form  a  close 
paling  or  barrier  when  in  place. 

The  weirs  on  the  river  Seine  in  France  differ  materially 
from  the  open  Indian  weirs.  They  consist  of  a  series  of  iron 
frames  of  trapezoidal  cross-section,  somewhat  similar  in  shape 
to  the  frames  of  the  open  wooden  flashboard  weirs  of  Cali- 


OPEN  MASONRY    WEIRS,  INDIAN    TYPE. 


109 


fornia.  On  these  frames  rest  a  temporary  footway,  and  on 
their  upper  side  is  placed  a  rolling  curtain  shutter  or  gate 
which  can  be  dropped  so  as  to  obstruct  the  passage  of  water 
across  the  entire  channelway  of  the  stream,  or  can  be  raised 
to  such  a  height  as  to  permit  the  water  to  flow  under  them.  In 


FIG.  20. — VIEW  OF  OPEN  WEIR  ON  RIVER  SEINE,  FRANCE. 


times  of  flood  the  curtains  can  be  completely  raised  and  re- 
moved on  a  temporary  track  to  the  river  banks,  the  floor  and 
track  can  then  be  taken  up,  leaving  nothing  but  the  slight  iron 
frames,  which  scarcely  impede  the  discharge  of  the  river  and 
permit  abundant  passageway  of  the  floods  over,  around,  and 
through  them  (Fig.  20). 


m 


t 


WOODEN   CRIB  AND  ROCK    WEIRS.  Ill 

132.  Wooden  Crib  and  Rock  Weirs.— This  type  of  weir 
is  generally  built  where  the  bed  and  banks  of  the  river  are  of 
heavy  gravel  and  bowlders,  or  of  solid  rock,  and  it  may  be 
employed  for  diversions  of  greater  height  than  is  possible  with 
open  weirs.  Crib  weirs  consist  essentially  of  a  framework  of 
heavy  logs,  drift-bolted  or  wired  together,  and  filled  with 
broken  stone  and  rocks  to  weight  and  keep  them  in  place. 
Such  works  may  be  founded  by  sinking  a  number  of  cribs  one 
on  top  of  the  other  to  a  considerable  depth  in  the  gravel  bed 
of  the  stream,  or  they  may  be  anchored  by  bolting  them  to 
solid  rock.  They  may  consist  of  separate  cribs  built  side  by 
side  across  the  stream  and  fastened  firmly  together  as  in  the 
case  of  the  weir  at  the  head  of  the  Arizona  canal,  or  they  may 
be  made  as  one  continuous  weir,  as  in  the  case  of  the  structures 
at  the  heads  of  the  Kraft  Irrigation  District  canal  in  California, 
and  the  Bear  river  canal  in  Utah.  After  its  completion  the 
weir  is  planked  over  on  its  exposed  faces  and  forms  one  con- 
tinuous wall  across  the  channel  of  the  stream. 

The  weir  at  the  head  of  the  Arizona  canal  (PL  IV)  con- 
sists of  crib  boxes  of  hewn  logs  about  9  by  9  feet,  the  logs 
being  fastened  with  drift-bolts,  and  the  whole  wired  together 
and  filled  with  rocks.  This  weir  was  constructed  by  laying 
mudsills  in  a  trench  excavated  in  the  bed  of  the  stream,  and  on 
these  was  built  up  the  cribwork.  In  the  central  and  deepest 
portion  of  the  river  channel  the  weir  was  sunk  to  a  depth  of 
33  feet  in  the  gravel  bed  of  the  stream,  while  its  crest  is  every- 
where 10  feet  above  mean  low-water.  The  base  of  this  weir 
in  the  deepest  part  of  the  channel  is  from  36  to  48  feet  in 
width  parallel  to  the  course  of  the  stream,  and  the  mudsills, 
which  are  8  by  12  by  48  feet,  were  wired  together  with  i-inch 
cable  to  act  as  a  hinge  between  the  sections.  Each  section 
was  floored  and  cribbed  and  built  up  as  a  box,  only  the  alter- 
nate sections  being  closed  at  first,  the  others  being  left  open 
for  the  passage  of  water.  These  openings  were  planked  on 
the  bottoms  and  sides.  The  alternate  sections  were  closed  by 
dropping  timbers  into  place.  Instead  of  bringing  up  the  face 
batter,  as  is  ordinarily  done,  the  weir  was  built  in  four  sections 


112 


HEADWORKS  AND  DIVERSION    WEIRS. 


transversely  to  its  axis  (Fig.  21).    The  first  section  consisted  of 
two  rows  of  cribs,  the  upper  faces  of  which  were  given  a  slight 


'4       r        » 

FIG.  2T. — CROSS-SECTION  OF  ARIZONA  WEIR. 

batter,  and  on  them  silt  has  since  deposited  and  helps  to  weight 
the  structure.  Immediately  below  the  crest  and  with  its  upper 
surface  2J-  feet  lower  is  another  row  of  cribs  which  drop  off  2j 
feet  to  the  third  row  of  cribs,  below  which  at  a  distance  of  2^ 
feet  still  lower  are  a  couple  of  depths  of  swinging  cribs  wired 
to  the  projecting  part  of  the  dam.  The  whole  of  this  upper 
surface  is  planked  over  and  forms  a  series  of  steps  upon  which 
the  water  falls,  its  force  being  thus  broken. 

The  crib  weir  at  the  head  of  the  Bear  river  canal  in  Utah 


FIG.  22. — CROSS-SECTION  OF  BEAR  RIVER  WEIR. 

is  370  feet  in  length  on  its  crest,  which  is  17^  feet  in  maximum 
height  above  the  river  bed,  while  the  greatest  width  at  its  base 
parallel  to  the  course  of  the  stream  is  38  feet  (Fig.  22).  The 
up-stream  face  has  a  slope  of  I  on  2  while,  that  of  the  down- 


WOODEN   CRIB   AND  ROCK    WEIRS.  113 

stream  face  is  I  on  J,  the  water  falling  on  a  wooden  apron  an- 
chored by  bolts  to  the  bed-rock  of  the  river.  This  weir  con- 
sists of  heavy  10  by  12  timbers,  drift-bolted  to  the  rock  and 
firmly  spiked  together.  The  interstices  between  these  timbers 
are  filled  with  broken  stone,  and  it  is  backed  by  silt  deposited 
from  the  river. 

Sometimes  crib  weirs  are  founded  on  piles,  as  in  the  case  of 
the  weir  across  Stony  creek,  at  the  head  of  the  Kraft  Irrigation 
District  canal.  This  is  composed  of  timber  cribs  sheathed  with 
3  inches  of  plank  on  the  up-stream  face  and  7  inches  on  the 
lower  face,  and  it  rests  on  two  rows  of  piles  driven  across  the 
entire  width  of  the  stream,  6  feet  apart  between  centres.  One 
of  these  rows  of  piles  is  driven  to  a  depth  of  12  feet  under  the 
toe  of  the  apron,  while  8  feet  below  this  is  a  row  of  sheet 
piling  and  22  feet  above  the  upper  row  of  piles  is  another  row 
of  sheet  piling,  both  of  these  being  of  4-inch  double  piling  8 
feet  in  length  or  driven  to  bed-rock. 

The  crib  weir  across  the  Connecticut  river  at  Holyoke, 
Mass.,  is  about  1017  feet  in  length,  its  ends  abutting  against 
heavy  masonry  wings  at  either  extremity.  Between  these 
the  crib  weir  is  composed  of  12  by  12  timbers,  built  in  such  a 
way  as  to  present  on  the  upper  face  a  surface  of  planking 
inclined  at  an  angle  of  21  degrees  to  the  horizon.  These  tim- 
bers are  separated  by  transverse  timbers  at  distances  of  6  feet 
apart,  and  the  whole  is  drift-bolted  to  the  solid  rock  of  the 
channel.  The  cribwork  is  filled  with  loose  stone  to  a  height 
of  about  10  feet,  and  the  upper  surface  of  the  weir  is  planked 
over.  On  the  upper  toe  of  the  weir  rests  a  bed  of  concrete 
to  prevent  seepage,  and  over  this  is  a  filling  of  gravel 
to  a  height  of  about  10  feet  (Fig.  23).  The  down-stream 
face  of  this  structure  consists  of  an  apron  or  rollerway  of 
similar  crib  timbers,  a  little  more  substantially  built.  Origi- 
nally the  down-stream  face  was  nearly  vertical,  but  the  water 
soon  so  undermined  the  structure  that  it  was  found  necessary 
to  add  this  rollerway  to  prevent  its.  destruction.  This  addi- 
tion has  the  same  slope  on  the  down-stream  face  as  has  the 
up-stream  face  for  a  distance  of  about  50  feet  below  the 


HEADWORKS  AND   DIVERSION    WEIRS. 


CONSTRUCTION   OF  CRIB    WEIRS.— COMPOSITE    WEIRS.   11$ 

crest  of  the  weir,  at  which  point  it  falls  away  vertically,  its  end 
being  nearly  level  with  the  surface  of  the  river,  though  its 
vertical  height  at  this  point  is  about  25  feet.  As  the  water 
rolling  over  this  drops  immediately  into  a  water  cushion  of 
considerable  depth,  no  injury  is  done  the  structure  from  its 
impact. 

133.  Construction  of  Crib  Weirs.— A  crib  weir  should 
never  be  left  hollow,  as  was  the  upper  part  of  the  Holyoke 
weir,  but  should  be  completely  filled  in  with  gravel  or  rock. 
Many  engineers  advise  against  rock  filling,  as  this  permits  the 
passage  of  air  to  the  wood,  and  thus  promotes  its  decay.     The 
action  of  air   in   causing   decay   is   still    more    marked  if  the 
weir  is  left  hollow.     Gravel  well  puddled  around   the  wood- 
work becomes  air-tight,  and  protects  every  timber  which  it 
encases.     This  material  is  therefore  the  most  desirable  filling. 
No  timbers  should  butt  on  top  of  the  course  next  beneath,  as 
this  gives  each  timber  6-inch  bearing  at  the  most,  and  if  the 
lower  timbers  become  decayed  the  strength  of  the  bearing  is 
speedily  reduced.     The  shape  of  such  a  weir  should  always  be 
such  as  to  prevent  the  water  which  falls  over  it  from  excavating 
beneath  its  toe,  especially  if  the  foundation  is  of  gravel  or  soft 
rock.    In  such  cases  a  roller  apron  should  be  built,  backed  still 
lower  down  by  a  horizontal  apron  which  will  take  up  the  scour- 
ing force  of  the  water.    Even  on  a  firm  rock  foundation  a  clear 
overfall  should  not  be  given  unless  a  deep  water  cushion  can 
be  furnished  or  the  bed  of  the  river  can  be  laid  dry  for  exam- 
ination and  the  repair  of  the  weir. 

134.  Composite    Gravel    and    Rock  Weir. — There    are 
several  varieties  of  mixed  weirs   other  than    those    described 
which  have  given  satisfaction  in  the  West.     One  of  these  is 
built  across    the  Lower   Fox  river  at    Little    Kukuna.     The 
foundation  of  this  weir  (Fig.  24)    is  of   gravel  and  loose   ma- 
terial, and  the  structure  is  held  in  place  by  two  parallel  rows 
of  piling  driven  across  the   entire  width  of  the  stream.     One 
of  these  rows  runs  through  the  centre  of  the  weir,  its  sum- 
mit being    on   a   level  with   the  crest ;    the  other  is   10  feet 
further  down-stream,  and  forms  the  edge  of  the  lower  portion 


i6 


HEADWORKS  AND  DIVERSION    WEIRS. 


of  the  apron.  These  piles  were  driven  14  feet  into  the  gravel 
and  bowlder  bed,  and  the  two  rows  were  braced  together  by 
10  by  10  timbers  and  the  intervening  space  filled  with  broken 
stone.  On 'the  upper  side  of  the  upper  row  4-inch  planking 
was  spiked  to  within  2  feet  of  the  river  bed,  below  which  sheet 
piling  was  driven  against  this  piling  4  feet  into  the  gravel  bed 


FIG.  24  — CROSS-SECTON  OK  LITTLE  KUKUNA  WHIR. 

to  prevent  seepage.  On  the  upper  side  of  this  barrier,  against 
the  planking  and  sheet  piling,  alternate  layers  of  clay  and  gravel 
were  laid,  at  a  slope  of  I  on  i£,  and  on  top  of  this  was  placed 
a  thickness  of  i^  feet  of  loose  stone,  the  whole  being  faced 
with  large  flat  stones  4  inches  thick.  The  top  surface  of  the 
down-stream  face  between  the  two  rows  of  piling  has  an  incli- 
nation of  about  i  on  3-J-,  and  is  faced  with  4  inches  in  thickness 
of  planking,  below  which  the  loose  rock  is  given  a  slope  of  I 
on  \\. 

135.  Scouring  Effect  of  Falling  Water. — In  the  con- 
struction of  weirs  various  subterfuges  have  been  employed  to 
deliver  the  falling  water  so  quietly  that  it  shall  not  erode  the 
stream-bed  below.  The  erosive  force  of  falling  water  is  such 
that  it  is  capable  of  wearing  away  even  the  hardest  rock.  The 
principal  forms  which  have  resulted  from  the  endeavor  to  re- 
duce this  action  are:  I,  aprons,  2,  sloping  roller-ways,  3,  ogee 
curves  to  the  lower  side  of  the  weir,  and  4,  water  cushions.  Each 
of  these  forms  has  its  advocates,  and  each  is  especially  adapted 


WEIR   APRONS.  II/ 

to  certain  conditions,  dependent  chiefly  upon  the  height  of  over- 
fall and  the  character  of  the  material  of  which  the  stream-bed 
is  composed.  Under  similar  conditions  aprons  are  employed  in 
all  countries.  Ogee  shapes  appear  to  have  originated  in  India, 
and  are  very  popular  there.  They  have  been  adopted  to  a 
limited  extent  in  this  country. 

136-  Weir  Aprons. — Where  the  foundation  of  the  weir  is 
of  some  unstable  material,  as  earth,  sand,  or  gravel,  an  apron  is 
built  below  its  down-stream  toe.  These  aprons  are  made  of 
wood,  of  dry-laid  masonry,  or  of  masonry  in  cement.  They 
form  a  substantial  artificial  flooring  to  the  stream-bed  on  which 
the  force  of  the  falling  water  is  taken  up,  thus  protecting  it 
from  erosion  and  preventing  undercutting  of  the  weir.  Where 
an  apron  is  employed,  the  weir  depends  on  its  efficient  con- 
struction and  careful  maintenance  for  its  security.  Such  works 
are  built  of  masonry  in  the  most  substantial  manner  in  India, 
where  a  rough  general  rule  is  to  give  the  masonry  apron  a 
thickness  equal  to  one  half  and  a  length  parallel  to  the 
stream  channel  equal  to  from  three  to  four  times  the  vertical 
height  of  the  obstructive  part  of  the  weir.  Beyond  this  a  loose 
stone  apron  is  generally  added,  with  a  length  equal  to  one  and 
one  half  times,  and  a  depth  equal  to  two  thirds  of  the  height  of 
the  weir.  Another  rule  adopted  in  India  is  to  give  the  apron 
a  width  equal  to  from  six  to  eight  times  the  square  root  of  the 
maximum  depth  of  water  above  the  weir  crest,  and  a  thickness 
equal  to  one  fifth  to  one  fourth  of  the  overfall  height  of  the 
weir  plus  the  depth  of  water  on  the  crest. 

According  to  the  American  standards  both  of  these  rules 
seem  to  give  unnecessarily  substantial  results.  With  us  wooden 
aprons  are  generally  employed  which  rarely  exceed  from  2  to 
6  feet  in  thickness  for  the  greatest  height  of  overfall.  Aprons, 
however,  cannot  be  used  with  security  with  weirs  in  which  the 
drop  is  considerable.  No  limit,  other  than  that  of  expense, 
can  be  set  to  the  height  for  which  aprons  are  serviceable, 
for  a  point  is  ultimately  reached  where  an  ogee-shaped  or 
rcllerway  weir  or  a  water-cushion  will  be  less  expensive  and 
more  serviceable. 


Il8  HEADWORKS  AND   DIVERSION    WEIRS. 

137.  Rollerway  and  Ogee-shaped  Weirs. — Ogee-shaped 
weirs  probably  originated  as  a  development  of  roller  aprons. 
The  first  ogee  weirs  of  any  magnitude  were  those  built  on 
the  falls  in  the  eastern  Jumna  canal  in  India.  The  original 
sloping  apron  or  rollerway  is  still  largely  employed,  the  chief 
objection  to  it  being  the  amount  of  material  required  in  its 
construction  and  its  consequent  cost.  Such  structures  are  the 
weirs  of  the  Soane  and  Agra  canals,  illustrated  in  PL  III. 
In  these  the  lower  slope  of  the  weir  is  made  extremely  flat,  so 
that  the  friction  of  the  water  rolling  over  it  shall  retard  its 


FIG.  25.— DIAGRAM  OF  OGEE  CURVE. 

velocity  and  diminish  its  erosive  action.  In  our  own  country 
a  similar  long  sloping  rollerway  is  that  on  the  Holyoke  weir 
(Fig.  23). 

The  ogee  shape  is  an  improvement  on  the  rollerway.  It 
reduces  to  a  minimum  the  amount  of  material  required,  while 
producing  nearly  the  same  effect.  The  object  of  the  ogee 
shape  is  to  cause  the  water  to  slide  instead  of  to  fall  over  the 
weir,  and  the  exact  moment  when  water  ceases  to  slide  and 
commences  to  fall  is  shown  by  its  losing  its  bluish  color  and 
commencing  to  become  whitish.  The  ogee  curve  is  best 
understood  from  the  accompanying  diagram  (Fig.  25). 
Bisect  AE,  and  from  the  point  of  bisection  at  A  draw  a  per- 
pendicular cutting  the  perpendicular  let  fall  from  A  at  C. 
Join  CE  and  prolong  this  line  until  it  cuts  the  perpendicular 


WA  TER-  CUSHIONS.  1  1  9 

projected  on  B  at  D.     From  the  points  C  and  D  as  centres, 
draw  the  curves  of  the  ogee 


A  good  example  of  ogee-shaped  weir  is  shown  in  plate  V. 

138.  Water-cushions.  —  The  principle  involved  in  the 
water-cushion  is  that  which  nature  has  laid  down  for  herself 
on  all  natural  falls,  namely,  that  of  having  a  deep  enough  cis- 
tern below  the  fall  to  take  up  the  shock  of  the  falling  water 
and  reduce  its  velocity  to  the  normal.  It  has  been  noticed 
below  cataracts  and  falls,  for  instance,  that  they  erode  a  cistern 
the  depth  of  which  bears  a  certain  relation  to  the  height  of  the 
fall.  The  method  of  constructing  a  water-cushion  is  not  to 
excavate  such  a  cistern  below  the  weir,  but  to  create  a  corre- 
sponding depth  by  building  a  subsidiary  weir  below  the  upper 
weir.  This  subsidiary  weir  backs  the  water  up  against  the 
lower  toe  of  the  main  weir  to  the  required  depth,  at  the  same 
time  practically  reducing  the  height  of  the  fall  by  the  height 
of  the  subsidiary  weir. 

It  is  difficult  to  find  any  set  rule  for  determining  the  depth 
of  water-cushion  for  a  given  height  of  fall.  From  observa- 
tions of  several  natural  waterfalls  it  has  been  discovered  that 
the  height  of  fall  is  to  the  depth  of  the  water-cushion  as  from 
5  or  7  to  I.  In  an  experimental  fall  constructed  on  the  Bari 
Doab  canal  in  India  it  was  found  that,  with  a  height  of  fall  to 
a  depth  of  water-cushion  as  3  to  4  the  water  had  no  injurious 
effect  on  the  bottom  of  the  well.  On  canals  where  the  height 
of  fall  is  not  great  it  has  been  discovered  that  the  depth  of 
the  water-cushion  may  be  approximately  determined  from  the 
formula  D  =  c  Vh3  Vd,  in  which  D  represents  the  depth  of  the 
water-cushion  below  the  crest  of  the  retaining  wall  ;  c  is  a  coeffi- 
cient the  value  of  which  is  dependent  on  the  material  which  is 


120  HEADWORKS  AND  DIVERSION    WEIRS. 

used  for  the  floor  of  the  cushion  and  varies  between  .75  for 
compact  stone  and  1.25  for  moderately  hard  brick;  //  is  the 
height  of  the  fall,  and  d  is  the  maximum  depth  of  water  which 
passes  over  the  crest  of  the  weir.  The  breath  of  the  floor  or 
the  bottom  of  the  cistern  of  the  water-cushion  parallel  to  the 
stream  channel  is  dependent  on  the  section  of  the  weir  and 
will  not  exceed  8</and  should  not  be  less  than  6d.  A  rule  laid 
down  for  determining  the  dimensions  of  water-cushions  and 
their  cisterns  on  the  smaller  canals  in  India  is  that  the  depth 
of  the  cistern  at  the  foot  of  the  weir  shall  equal  one  third  of 
the  height  of  the  fall  plus  the  depth  of  water.  Thus  on  a  fall 

4  feet  deep  on   a  canal  carrying  5   feet   of  water  the  cistern 
depth    will   equal   %(4+$)  =  3  feet.      The    minimum    cistern 
length  is  equal  to  three  times  the  depth  from  the  drop-wall  to 
the  reverse  slope  of  the  cistern,  which  latter  will  be  I  in  5. 
The  width  of  the  cistern  must  be  twice  the  mean  depth  of  the 
water  in  the  channel. 

On  the  Ganges  canal  it  was  found  that  the  ogee  form  of 
weir  was  not  entirely  satisfactory.  The  shock  of  the  falling 
water  proved  so  great  as  to  materially  injure  the  structure, 
and  all  of  these  ogee  falls  have  since  been  remodelled  in  such 
a  manner  as  to  form  water-cushions.  Thus  on  falls  15  feet 
high  the  ogee  has  been  cut  so  as  to  give  first  a  vertical  fall  of 

5  feet  to  a  short  level  bench  10  feet  in  length,  then  a  vertical 
drop    of  10  feet  ending  in  a  shallow  water-cushion  the  floor 
of  which    is    of    masonry  4    feet    in    thickness.     It   may  be 
generally   asserted    that   experience    in   India  has  proved  un- 
favorable   to   the    ogee    form.     In    this    country  a    few    ogee 
weirs  have  been  designed  and  constructed  with  a  partial  ogee 
curve  to    the   lower   face,   the   water   dropping  into  a  water- 
cushion.     The  most  notable  of  these  is  the  great  weir  at  the 
head   of  the  Turlock  and  Modesta   canals   in   California  (Ar- 
ticle 276).     A  water-cushion  15  feet  in  depth  is  obtained  below 
this  weir  by  the  construction  of  a  subsidiary  weir  20  feet  in 
height,  placed  at  a  distance  of  200  feet  below  the  main  weir. 
The  height  of  overfall  from  the  main  weir  is  98  feet,  thus  giv- 
ing a  ratio  of  depth  of  water-cushion  to  height  of  overfall  of 


MASONRY    WEIRS.  121 

about  I  in  6.  In  the  case  of  this  weir,  however,  its  down- 
stream face  is  not  made  vertical,  but  is  made  somewhat  after 
the  design  which  would  be  obtained  by  using  one  of  the 
gravity  formulas  and  adding  to  this  sufficient  material  to  pro- 
duce the  ogee  curve. 

The  Indian  method,  which  has  proved  very  satisfactory  in 
practice,  is  well  illustrated  in  the  Vir  weir  (Article  146)  and  the 
Betwa  weir  (Article  275).  In  each  of  these  the  water  is  per- 
mitted a  clear  vertical  overfall  to  the  water-cushion,  the  weight 
necessary  to  give  the  weir  stability  being  obtained  by  increasing 
its  cross-section  on  the  up  stream  side.  In  both  of  these  cases 
subsidiary  weirs  are  constructed  at  some  distance  below  the 
main  weir  in  the  rock  bed  of  the  river,  which  back  up  the  water 
to  the  required  height  on  the  toe  of  the  main  weir.  A  sub- 
sidiary weir  of  a  form  somewhat  similar  to  that  below  the  Vir 
weir  is  illustrated  in  Fig.  84.  This  weir  is  employed  below  the 
main  escape  weir  of  the  Periar  dam  in  India  to  form  a  water- 
cushion  on  which  the  floods  fall. 

139.  Masonry  Weirs. — If  it  is  intended  that  the  weir  shall 
be  permanent,  only  masonry  and  iron  should  be  used  in  its 
construction.  It  is  frequently  necessary,  however,  to  build 
weirs  of  less  durable  material,  the  object  being  to  economize 
on  the  first  cost.  Masonry  weirs  may  be  built  of  concrete 
throughout ;  of  uncoursed  rubble  in  cement :  of  ashlar  ;  of  brick  ; 
and  of  various  combinations  of  these,  including  loose  packed, 
uncemented  rubble  retained  in  place  by  masonry  walls  (Articles 
256  to  260). 

The  principal  classification  of  masonry  weirs  is  dependent 
on  the  foundation.  Where  practicable  such  structures  should 
only  be  founded  on  firm  rock,  but  occasionally  the  depth  of 
this  below  the  surface  is  so  great  as  to  render  it  necessary  to 
found  the  weir  on  gravel  or  sand.  Masonry  weirs  may  be 
classified  according  to  the  superstructure  as  follows:  first, 
simple  weirs  with  a  clear  overfall  to  the  stream-bed  ;  second, 
simple  weirs  with  clear  overfall  to  an  artificial  apron  ;  third, 
weirs  with  rollerway  on  lower  face  ;  fourth,  weirs  with  heavy 


122  HEADWOKKS  AND   DIVERSION    WEIRS. 

cross  section  and  ogee  shape ;  fifth,  weirs  with  clear  fall  ta 
water-cus,hion. 

140.  Masonry  Weirs  founded  on   Piles. — In   the    con- 
struction of  masonry  weirs  in  gravel  or  earth,  several  methods 
have  been   employed   for   obtaining  a  permanent  foundation. 
In  America  it  is  usual    to    found  the  weir   on  wooden    piles 
driven    deep    into    the    river-bed.      Occasionally   hollow    iron 
piles   have    been    sunk  by  dredging    from  their  interiors  and 
filling  them  with  concrete.     In  a  few  instances  cribs  and  cais- 
sons   have  been    sunk    for    foundations.     In    India   the   usual 
foundation  in  unstable  material  is  the  "well"  (Article  143). 

The  weir  of  the  Norwich  Water  Power  Company  across 
the  Shetucket  river  in  Connecticut  is  a  good  example  of  a 
weir  founded  on  piles.  The  bed  of  the  river  at  the  site  of 
the  weir  is  composed  of  gravel  containing  small  bowlders  and 
is  30  feet  or  more  in  depth.  This  weir  (Fig.  26)  is  15  feet 
wide  at  the  base  and  7-J  feet  wide  on  top,  its  maximum  height 
being  about  20  feet.  It  is  constructed  of  rubble  masonry  with 
a  cut-stone  coping-wall.  The  lower  slope  is  covered  with  one 
foot  of  concrete  faced  with  planking  secured  to  it  with  long 
iron  bolts.  The  up-stream  face  has  a  batter  of  12  on  5  and 
is  backed  by  an  earth  filling  having  a  slope  of  about  I  on  i-J, 
which  reaches  to  the  crest  of  the  weir.  As  this  structure 
is  founded  on  gravel,  there  was  great  danger  that  the  flood 
waters,  which  pass  over  it  to  a  depth  of  14  feet,  might  under- 
mine it,  accordingly  a  heavy  timber  apron  was  built,  projecting 
down-stream  for  22  feet,  while  the  last  8  feet  of  the  apron  has 
an  upward  pitch  designed  to  throw  the  water  out  and  form  a 
shallow  water-cushion  of  about  a  foot  in  depth.  This  apron  is 
composed  of  two  thicknesses  of  timber  the  intervening  space 
being  filled  with  sand  and  loose  stone.  The  entire  structure 
is  founded  on  anchor  piling  and  is  protected  by  sheet  piling 
from  10  to  12  feet  in  depth. 

141.  Masonry  Weir  founded  on   Piles  and  Cribs.— On 
the  Chicopee  river  in  Connecticut,  is  a  weir  built  at  a  place 
where  the  stream-bed  is  partly  of  rock  and  partly  of  deep  gravel. 
Its  cross-section  is  the  same  both  where  it  rests  on  rock  and  on 


MASONRY   WEIR  FOUNDED  ON  PILES  AND  CRIBS.       1 23 

gravel,  and  is  similar  to  that  of  the  weir  just  described.  Where 
the  river-bed  is  composed  of  gravel  the  weir  rests  directly  on 
a  depth  of  3  feet  of  cribwork,  composed  of  squared  timbers 
laid  horizontally  and  transversely  about  2  feet  apart,  the  in- 
terstices being  filled  with  broken  stone.  Below  this  portion 
of  the  weir  and  connected  with  its  timber  foundation  is  an 
apron  10  feet  in  length  which  rests  on  anchor  piles,  its  lower 
extremity  being  protected  by  a  row  of  sheet  piling,  while  two 
rows  of  sheet  piling  extend  along  the  edges  of  the  timber 
foundation  below  either  toe  of  the  weir.  This  apron  is  of  the 
same  general  character  as  the  timber  foundation,  its  total 


Fi<;.  26.  — CROSS-SECTION  OF  NORWICH  WATER  POWER  COMPANY'S  WEIR. 

thickness  being  5  feet.  The  crest  of  the  weir  is  from  15  to  16 
feet  above  the  river-bed,  and  it  is  composed  of  rubble  masonry 
surmounted  by  an  inclined  coping  of  ashlar  between  6  and  7 
feet  in  width.  The  upper  face,  of  the  weir  has  a  batter  of  7 
on  i  and  the  down-stream  slope  a  batter  of  3  on  I. 

142.  Masonry  Weir  founded  on  Cribs. — One  of  the 
most  interesting  and  largest  masonry  weirs  founded  on  un- 
stable soil  is  that  on  the  middle  branch  of  the  Croton  river, 
in  New  York.  This  work  was  constructed  essentially  for  water- 
storage  purposes  but  acts  also  as  a  weir  since  the  flood  waters 
of  the  stream  pass  over  it.  The  construction  of  this  weir  is 
peculiarly  composite,  a  large  portion  of  it  resting  on  firm  rock, 


I24 


HEADWORKS  AND   DIVERSION    WEIRS. 


MASONRY    WEIR   FOUNDED   ON   CRIBS.  125 

while  the  remainder  is  fouuded  on  a  stratum  of  alluvial  soil 
containing  bowlders.  The  piers  (Plate  V)  are  of  timber  crib- 
work,  the  walls  of  which  are  connected  by  ties  and  the  whole 
filled  with  stone.  These  cribs  are  planked  on  top,  and  upon 
them  are  built  two  smaller  wooden  piers,  similar  in  all  respects 
to  the  first  and  likewise  planked  over.  The  space  between 
was  then  filled  with  concrete  and  the  top  of  the  piers  con- 
nected by  ties  of  timber.  An  additional  pier  similar  to  those 
just  described  was  built  below  the  first  and  filled  with  con- 
crete. Upon  this  foundation  the  masonry  weir  was  con- 
structed.  It  consists  of  stone  set  in  hydraulic  cement,  the 
main  body  being  laid  in,  horizontal  layers.  The  facing  is  of 
finely  cut  granite  ashlar  well  bonded  together  and  inclining  at 
right  angles  to  the  curved  face  of  the  weir. 

This  structure  is  50  feet  in  maximum  height  and  76  feet  in 
maximum  width  at  the  base.  Its  up-stream  slope  is  vertical 
for  23^  feet,  below  which  it  is  broken  into  two  vertical  benches 
by  the  piers  just  mentioned.  It  is  backed  behind  by  an  earth 
embankment  having  a  very  low  and  flat  slope.  The  down- 
stream face  has  an  ogee  curve  similar  to  that  which  would  be 
assumed  by  the  water  flowing  over  it.  The  crest  of  this  face  is 
convex  with  a  radius  of  10  feet,  below  which  is  a  reverse  or 
concave  curve  with  a  radius  of  55  feet.  Below  the  lower  end 
of  this  weir  is  built  a  raised  apron  55  feet  in  total  length  and  con- 
nected with  the  main  weir.  The  rise  of  this  apron  is  I  in  iij, 
and  the  amount  of  this  rise  is  2^  feet,  giving  a  water-cushion 
of  this  depth  in  the  lower  part  of  the  apron.  The  latter  con- 
sists of  five  sets  of  cribs,  the  two  nearest  the  weir  being  filled 
with  concrete  and  the  remainder  with  broken  stone.  They 
are  of  12  by  12  timbers  and  are  covered  with  planking.  At  a 
distance  of  300  feet  from  the  extremity  of  this  apron  is  built 
a  secondary  weir  of  crib  timber  filled  with  broken  stone. 
The  object  of  this  secondary  weir  is  to  divide  the  head  of 
water,  thus  causing  it  to  fall  in  two  steps,  the  first  38  feet  in 
height  to  the  lowest  part  of  the  apron,  and  the  second  15  feet 
in  height  over  the  secondary  weir  to  the  stream  bed.  This 
secondary  weir  answers  the  additional  purposes  of  creating  a 


126         ^         HEADWORKS  AND  DIVERSION    WEIRS. 

shallow  water-cushion  at  the  foot  of  the  main  weir,  and  of 
protecting  the  timber  of  the  apron  from  deterioration  by  keep- 
it  under  water.  Near  the  left  shore  of  this  weir  is  a  wasteway 
by  means  of  which  the  water  can  be  drawn  off  from  this 
water-cushion. 

143.  Masonry  Weirs  founded  on  Wells. — This  class  of 
weir  is  as  yet  peculiar  to  India,  where  it  is  built  on  sand  or 
gravel  stream-beds.     In  PI.  Ill  are  illustrated  several  examples 
of  these  structures,  while  that  built  across  the  Soane   river  is 
described  in  Article   131.     They  consist  essentially  of  one  or 
more  walls  of  masonry  running  across  the  entire  width  of  the 
stream  and  founded  on  wells,  while  the  space  between  these  is 
filled  in  with  loose  packed  stone.     The  slopes  of  these  weirs 
are  generally  long  and  low,  varying  between  vertical  and  I  on 
3  to  5  on  the  upper  face,  but  on  the  lower  face  ranging  from  I 
to  10  to  20.     In  the  case  of  the  weir  across  the  Ganges  river 
at  the  head  of  the  lower  Ganges  canal,  the  main  obstruction  to 
the  stream  channel  is  a  masonry  wall  founded  on  wells.     On 
the  lower  or  down-stream   face,  however,  instead  of  the  usual 
long  slope  there  is  a  vertical  drop  of  9^  feet.     The  top  width 
of  the  wall  is  7  feet,  and  the  water  falling  over  this  drops  to 
an  apron  nearly  150  feet  long  which  is  composed  of  masonry 
resting  on  four  rows  of  shallow  wells  for  a  distance  of  about 
40  feet,  below  which   a  loose  stone  apron  kept  in  place  by 
rows  of  wells  extends  for  the  remaining  1 10  feet. 

144.  Weirs  founded  on  Rock.     San  Diego  Weir. — One 
of  the   first   masonry  diversion  weirs  built  in  the  west  is  that 
on  the  San  Diego  river  in  California  at  the  head  of  the  San 
Diego  flume.     This  weir  (Fig.  27)  is  built  in  two  tangents,  the 
exterior  angle  of  which  points  up  stream.     At  a  distance  of  108 
feet  from  the  south  end  is  the  outlet  sluice,  beyond  which  the 
weir  is  reinforced  on  its  lower  side  by  a  great  mass  of  loose 
stone,  the  object  of  which  is  to  break  the  force  of  the  falling 
water.     At  a  distance  of  32  feet  beyond  the  outlet  sluice  is  an 
open  wasteway  20  feet  wide,  the  crest  of  which  is  4  feet  lower 
than  that  of  the  remainder  of  the  weir.     Fourteen  feet  beyond 
this  wasteway  is  another  which  is    165  feet  in  length,  its  crest 


SAN  DIEGO    WEIR— HENARES    WEIR. 


127 


being  at  the  same  height  as  that  of  the  first  described.  In 
the  bottom  of  the  weir  are  two  undersluices,  one  near  the 
centre  and  the  other  under  the  outlet  sluice,  and  respectively 
1 8  and  14  feet  below  the  crest  of  the  weir.  In  cross-section 
this  weir  is  35  feet  in  height,  5  feet  wide  on  top  and  16  feet 


Regulator 


,08' -*r-  -  32'-  -nt-  20'  -*-  14'   -it 65' 

FIG.  27. — PLAN,  ELEVATION,  AND  CROSS-SECTION  OF  SAN  DIEGO  WEIR. 

wide  at  the  bottom.  It  was  sunk  to  a  depth  of  from  15  to  25 
feet  in  the  gravel  bed  of  the  river,  its  crest  being  about  10  feet 
above  the  stream-bed. 

145.  Henares  Weir. — This  weir  is  at  the'  head  of  the 
Henares  canal  in  Spain.  As  shown  in  cross-section  (Fig.  28)  it 
is  23  feet  in  maximum  height,  its  upper  slope  having  a  batter 
for  the  lower  two  thirds  of  about  6  on  I,  and  for  the  upper 
third  of  12  on  I.  Its  top  width  is  3.14  feet,  its  thickness 
at  the  base  is  45.8  feet,  and  its  face  has  an  easy  flat  ogee- 
shaped  curve.  This  weir  is  390  feet  in  length  on  the  crest, 
being  curved  in  plan  and  running  obliquely  across  the  river  at 
a  tangent  to  the  axis  of  the  canal.  Its  body  is  composed  of 
concrete,  while  the  crest  and  lower  slope  are  faced  with  cut 
stone  blocks  alternating  in  headers  and  stretchers.  Great  care 
was  taken  in  the  construction  of  this  work  to  prevent  leakage. 


128 


HEADWORKS  AND  DIVERSION    WEIRS. 


This  was  obviated  by  cutting  a  channel  in  the  rock  along  the 
central  axis  of  the  weir  for  its  entire  length,  and  in  this  is  fitted 
a  line  of  stone,  half  bedded  in  the  rock  and  half  in  the  concrete 


FIG.  28.  — CROSS-SECTION  OF  HENARES  WEIR,  SPAIN. 

of  the  weir.  These  stones  were  built  into  the  rock  and  the  joints 
were  then  run  with  pure  cement.  In  the  sides  of  each  of  the 
four  upper  courses  of  stones  near  the  crest  of  the  weir  were 
cut  V-shaped  grooves,  and  expanding  horizontal  grooves  were 
cut  in  the  upper  and  lower  faces  of  each  stone,  forming  a  con- 
tinuous channel  which  was  filled  with  pure  cement  so  as  to 
form  a  tight  joint  between  each  stone.  As  the  bed  of  the 
river  was  uneven,  it  was  found  necessary  to  carry  down  the 
lower  portion  of  the  weir  as  an  apron  by  means  of  a  series  of 
blocks  of  stone  formed  in  steps,  the  last  of  which  is  firmly  em- 
bedded 3  feet  in  the  rock. 

146.  Appleton  Weir. — The  upper  weir  at  Appleton,  Wis- 
consin (Fig.  29),  across  the  lower  Fox  river  is  built  throughout 


FIG.  29.— CROSS-SECTION  OF  APPLETON  WEIR. 

of  dressed  rubble  limestone  with  the  exception  of  the  coping, 
which  is  of  ashlar.  This  weir  is  II  feet  in  maximum  height,  the 
total  height  of  overfall  being  about  10  feet.  It  is  15  feet  in 
width  at  its  base  and  4  feet  wide  on  the  crest,  the  down-stream 


VI R   WEIR— OTHER   MASONRY   WEIRS.  12$ 

slope  being  about  4  on  I,  while  the  up-stream  slope  is  nearly  i 
on  I.  Each  coping-stone  is  fastened  by  a  band  of  i-inch  round 
iron  to  a  hook  set  into  the  masonry  at  the  toe  of  the  weir,  and 
the  adjoining  coping  stones  are  fastened  to  each  other  by 
ij-inch  iron  strap  dowelled  into  the  stones.  In  this  way  a 
most  substantial  bondage  is  obtained  throughout  the  work. 

147.  Vir  Weir. — The  Vir  weir  at   the   head   of  the   Nira 
canal  in  India  is  built   of  uncoursed   rubble   masonry  and   is 
protected  by  a  water-cushion.     It  is  2340  feet  in  length,  43^- 
feet  in  height,  and  9  feet  wide  on  top,  arid  is  constructed   of 
uncoursed   rubble   masonry.     The  down-stream  slope  is  8  on 
I   for  20  feet  from  the  crest  and  6  on  I  for  the  remainder  of 
the  weir,  while  the  up-stream  face  has  a  uniform  batter  of  20 
on   I   and  at  no  place  is  the  mean  thickness  of  the  weir  less 
than  half  its  height.     This  weir  is  founded  on  solid  rock  and 
in  order  to  form  a  water-cushion  a  subsidiary  weir  is  provided 
2800  feet  below  the  main  weir.    This  subsidiary  weir  is  located 
in  a  narrow  portion  of  the  river  channel,  its   total  length  being 
615  feet,  its  height  24^-  feet,  while  its  crest  is  20  feet  lower 
than  that  of  the  main  weir,  thus  forming  a  permanent  water- 
cushion  20  feet  deep.    The  maximum  flood  which  is  estimated 
to  pass  over  this  weir  is  158,000  second-feet,  producing  a  depth 
of  32  feet  in  the  water-cushion  and  a  height  of  overfall  of  but 
8  feet. 

148.  Other  Masonry  Weirs. — A  masonry  diversion  weir 
which  is  different  from  any  of  those  described  is  that  across 
the  Pequannock  river  near  Newark,  New  Jersey.     This  weir 
(Fig.  30),  which  also  serves  for  purposes  of  storage,  is  built  of 
rubble  masonry,  coursed  and  dressed  on  its  faces  and  having 
an  ashlar  capstone.     That  portion  of  the  structure  which  acts 
as  a  dam,  since  flood  waters  do  not  pass  over  it,  is  38  feet  in 
maximum  height,  5  feet   10  inches  wide  on   top,  and   21   feet 
wide  at  the  base.     The  remainder  of  the  structure,  which  is 
built  as  an  overfall  weir,  is  set  nearly  at  right  angles  to  the 
main  dam  and  is  curved  with  a  radius  of  640  feet.     This  over- 
fall weir  is  22  feet  in  height,  its  crest  being  7  feet  below  that 
of  the  main  dam.     It  is  15  feet  in  width  at  the  base  and  5  feet 


HEADWORKS  AND   DIVERSION    WEIRS. 


wide  on  top,  its  lower  slope  on  the  up-stream  face  being 
vertical  for  7  feet,  above  which  it  has  an  inclination  of  3  on  I. 
The  down-stream  face  has  an  inclination  of  8  on  I  for  8  feet 
below  the  crest,  below  which  it  changes  to  about  5  on  I  for  8 
feet  more,  and  then  to  3  on  I.  The  result  of  this  is  to  give 
a  clear  overfall  to  the  bed-rock  below,  which  is  protected 


77z 


FIG.  30.— CROSS-SECTIONS  OF  NEWARK  DAM  AND  WEIR. 

by  a  trifling  depth  of  water  in  the  river  channel,  which  acts  as 
a  water-cushion  of  moderate  depth.  The  coping  stone  of  the 
overfall  weir  is  irregular  in  shape  and  is  made  continuous  by 
means  of  dowels  between  the  several  stones,  and  is  secured 
to  the  structure  by  anchors  let  into  the  masonry  which  hold 
down  the  dowels  every  12  feet. 

The  weir  across  the  Merrimac  river  at  Lawrence,  Massa- 
chusetts, appears  to  have  an  unnecessarily  heavy  cross-section 
(Fig.  31).  It  is  33  feet  in  maximum  height,  its  extreme 
breadth  at  the  base  being  35  feet.  The  down-stream  face  has 
a  batter  of  12  on  I,  and  the  structure  is  surmounted  by  a 
coping  stone  which  is  level  for  3  feet  and  then  slopes  up- 
stream with  a  batter  of  I  on  6  for  12  feet,  beyond  which  the 
weir  is  stepped  off  with  a  batter  of  I  on  I  to  within  about 


LAWRENCE    WEIR— DIVERSION  DAMS.  131 

10  feet  of  its  base,  which  latter  portion  is  vertical.  It  is  com- 
posed of  rubble  masonry  founded  on  firm  rock,  the  front  of  the 
dam  resting  against  the  edge  of  a  trench  excavated  in  the 
rock.  The  face  and  coping  of  the  weir  are  of  dressed  ashlar, 


« 3S' i._* 

FIG.  31. — CROSS-SECTION  OF  LAWRENCE  WEIR. 

headers  and  stretchers  being  dovetailed  together,  and  the 
coping  stones  are  dowelled  to  each  other  and  the  next  face 
stone  below.  The  body  of  the  weir  is  of  rough  rubble  in 
cement  and  is  backed  up  to  a  level  with  the  top  coping  by  an 
earth  filling  having  a  slope  of  I  on  6.  The  level  of  the  water 
may  be  raised  by  means  of  flashboards  16  feet  in  length  to  a 
height  of  3  feet. 

149.  Diversion  Dams. — There  are  several  structures  of 
considerable  magnitude  which,  from  the  functions  they  per- 
form, should  be  classified  as  diversion  weirs  rather  than  storage 
dams.  Prominent  among  these  are  the  Betwa  dam  in  India 
and  the  Folsom  and  Turlock  dams  in  the  United  States. 
The  two  latter  were  built  solely  for  purposes  of  diversion, 


I$2  HEADWORKS  AND   DIVERSION    WEIRS. 

while  the  former  serves  to  store  as  well  as  to  divert  water. 
These  works,  however,  are  of  such  magnitude  that  the  princi- 
ples involved  in  their  design  and  construction  are  essentially 
those  employed  in  designing  masonry  dams  for  water  storage, 
and  for  this  reason  they  will  be  described  among  masonry 
dams.  Another  variety  of  diversion  dam  employed  also  for 
storing  water,  is  represented  by  those  at  the  head  of  the 
Idaho  Mining  and  Irrigation  Company's  canal  and  the  Pecos 
canal  in  New  Mexico.  These  structures  are  both  of  com- 
posite character,  being  built  of  a  combination  of  earth  and 
loose  rock.  As  it  would  be  unsafe  to  permit  flood  waters  to 
pass  over  their  crests,  all  surplus  water  is  passed  around  them 
through  wasteways.  It  will  thus  be  seen  that  they  are  essen- 
tially storage  dams,  and  their  uses  for  purposes  of  diversion 
will  be  described  among  that  class  of  works  (Arts.  237  and  238). 


CHAPTER   XIII. 
SCOURING    SLUICES,    REGULATORS,   AND    ESCAPES. 

150.  Scouring  Sluices. — Scouring-  or  undersluices  are 
placed  in  the  bottom  of  nearly  every  well  constructed  weir  or 
dam,  at  the  end  immediately  adjacent  to  the  regulator  head. 
The  object  of  these  is  to  remove,  by  the  erosive  action  of  the 
water,  any  sediment  which  may  be  deposited  in  front  of  the 
regulator.  If  the  flow  in  the  stream  is  sufficiently  great  to 
permit  it,  these  scouring  sluices  are  kept  constantly  open  and 
thus  perform  their  functions  by  keeping  the  water  in  motion 
past  the  regulating  head  and  thus  preventing  the  silt  from  set- 
tling. If  sufficient  water  cannot  be  spared  to  leave  the  under- 
sluices constantly  open,  they  are  opened  during  flood  and  high 
waters,  and  by  creating  a  swift  current  are  effectual  in  re- 
moving silt  which  has  been  deposited  at  other  times. 

The  scouring  effect  of  sluices  constructed  in  the  body  of 
the  weir  is  produced  by  two  classes  of  contrivances ;  namely, 
by  open  scouring  sluices  and  by  undersluices.  The  open 
scouring  sluice  is  practically  identical  wkh  the  open  weir,  as 
the  latter  consists  of  scouring  sluices  carried  across  the  entire 
width  of  the  channel.  Where  the  weir  forms  a  solid  barrier 
to  the  channel  and  is  only  open  for  a  short  portion  of  its 
length  adjacent  to  the  canal  head,  the  latter  is  spoken  of  as  a 
scouring  sluice.  The  waterway  of  a  scouring  sluice  is  open 
for  the  entire  height  of  the  weir  from  its  crest  to  the  bed 
of  the  stream. 

Undersluices  are  more  generally  constructed  where  the  weir 
is  of  considerable  height  and  the  amount  of  silt  carried  in  sus- 
pension is  relatively  small.  In  these  the  opening  does  not  ex- 
tend as  high  as  the  crest  of  the  weir,  nor  does  the  sill  of  the 
sluiceway  necessarily  reach  to  the  level  of  the  stream-bed.  It 

133 


134      SCOURING   SLUICES,  REGULATORS,  AND   ESCAPES. 

is  chiefly  essential  that  its  sill  shall  be  as  low  as  the  sill  of  the 
regulator  head.  Undersluices  are  more  commonly  employed 
in  the  higher  structures,  such  as  weirs  and  dams  which  close 
storage  reservoirs  (Articles  288  and  289). 

Scouring  sluices  are  practically  open  portions  of  the  weir 
and  consist  of  a  foundation,  floorway,  and  superstructure.    The 


FlG.    32. — VlEW  OF   HlGHLINE    CANAI.   WEIR. 

floor  must  be  deep  and  well  constructed  and  carried  for  a  short 
distance  up-stream  from  the  weir  axis  and  for  a  considerable 
distance  below  it.  On  it  are  built  up  piers  grooved  for  the  re- 
ception of  planks  or  gates,  so  that  the  sluiceway  may  be  closed 
or  opened  at  will.  Scouring  sluices  have  been  built  in  very 
few  American  weirs,  the  most  substantial  structure  of  this  kind 
being  in  the  weir  at  the  head  of  the  Highline  canal  in  Colorado. 
In  Fig.  32  is  shown  a  view  of  this  wier  with  water  passing  over 
it,  and  in  the  foreground  is  the  scouring  sluice,  which  consists 


EXAMPLES   OF  SCOURING   SLUICES.  135 

or  two  masonry  piers  built  into  the  end  of  the  weir  and  form- 
ing its  abutment.  The  opening  between  these  is  the  entire 
height  of  the  structure  and  can  be  closed  by  four  sets  of  iron 
gates  which  slide  vertically  between  iron  columns.  These 
gates  are  each  4  feet  wide  between  centres  and  7  feet  in  height, 
and  can  be  raised  by  means  of  screws  turned  by  hand  wheels 
from  above,  and  their  sills  are  set  2  feet  below  the  level  of  the 
canal  head  gates.  This  structure,  however,  is  not  a  true  scour- 
ing sluice  in  that  it  is  not  at  the  end  of  the  weir  adjacent  to  the 
canal  head.  It  is  expected  to  clear  out  silt  which  has  deposited 
above  the  weir,  though  it  is  not  entirely  successful  in  produc- 
ing this  effect. 

151.  Examples  of  Scouring  Sluices. — At  the  head  of  the 
Monte  Vista  canal  in  Colorado  true  scouring  sluices  have  been 
constructed,  though  these  are  of  wood.  This  wier  (Fig.  16)  is 
built  across  the  gravel  bed  of  the  Rio  Grande,  and  is  founded 
on  piles  sunk  to  a  depth  of  10  feet.  The  wier  is  8  feet  in 
height  above  the  stream-bed  and  consists  of  an  earth  bank  16 
feet  in  length  at  the  end  furthest  away  from  the  canal  head, 
and  of  a  crib  weir  74  feet  in  length,  terminating  at  the  end  ad- 
jacent to  the  regulator  head  in  an  open  way  of  five  scouring 
sluices.  These  are  founded  on  piles,  and  the  stream-bed  be- 
neath is  floored  with  planking  to  form  an  apron  to  protect  it 
against  erosion.  The  openings  are  separated  by  upright  posts 
of  wood  reaching  to  the  crest  of  the  weir,  and  can  be  closed  by 
flashboards  dropped  between  grooves. 

An  excellent  example  of  masonry  scouring  sluice  is  fur- 
nished by  that  in  the  weir  at  the  head  of  the  Agra  canal  in 
India.  In  the  end  of  the  weir  adjacent  to  the  canal  head  are 
a  set  of  1 6  openings  having  a  clear  sluiceway  of  138  feet. 
These  openings  are  each  6  feet  in  width  between  the  upright 
piers  separating  them  and  are  10  feet  in  height,  surmounted 
by  a  masonry  superstructure  or  bridge  the  height  of  which  is 
19  feet  above  the  stream-bed.  The  object  of  this  bridge  is  to 
give  a  platform  from  which  to  operate  the  sluice  gates,  which 
are  of  wood,  well  braced  and  fastened  with  iron,  and  slide  ver- 
tically between  masonry  piers  each  2^  feet  in  thickness.  They 


136      SCOURING    SLUICES,  REGULATORS,  AND   ESCAPES. 

are  raised  by  means  of  a  winch  which  is  operated  from  above, 
travels  on  a  hand  car  on  rails  so  that  it  can  be  placed  at  will 
above  any  gate.  The  floor,  which  is  flush  with  the  stream-bed 
and  on  a  level  with  the  sill  of  the  regulator  head,  is  12  feet  in 
width  parallel  to  the  stream  channel  and  extends  8  feet  up- 
stream and  41  feet  down-stream  from  the  line  of  the  piers. 
When  these  gates  are  opened  all  the  heavy  silt-laden  waters  are 
carried  through  the  sluices,  and  when  closed  and  then  suddenly 
opened  the  scour  produced  by  the  rush  of  water  is  effective  in 
removing  the  silt  from  in  front  of  the  canal  head. 

152.  Automatic  Sluice  Gates. — Various  devices  have  been 
employed  whereby  the  gates  closing  scouring  sluices  may  be 
opened  rapidly  and  under  the  greatest  pressure  of  water  which 
may  be  brought  against  them  by  sudden  flood  rises.  But  few 
such  structures  have  been  built  in  this  country.  In  the  Dry 
creek  diversion  dam  on  the  line  of  the  Turlock  canal  is  a 
wasteway  closed  by  automatic  or  quick-dropping  gates.  These 
are  ten  in  number,  each  3  feet  wide  in  the  clear,  10  feet  in 
height,  and  are  constructed  of  wood.  They  are  hinged  at  the 
bottom  and  fall  outward  or  down-stream.  When  raised  they 
are  held  in  position  by  chains  attached  to  their  upper  edges 
and  fastened  to  the  piers  separating  them.  When  they  are  to 
be  dropped  these  are  detached  and  the  gates  fall  outward,  strik- 
ing on  a  shallow  water-cushion  built  in  the  floor  of  the  sluice- 
way beneath  them.  After  the  flood  has  subsided  the  gates 
can  again  be  raised  by  chains  and  geared  windlasses. 

In  nearly  all  the  scouring  sluices  so  far  described  the  mode 
of  operating  the  gates  is  from  a  superstructure  above  the  level 
of  the  highest  flood.  This  form  of  construction  is  expensive 
and  interferes  with  the  free  flow  of  water  by  stopping  and 
perhaps  choking  the  sluices  with  floating  brushwood  and  logs. 
To  remedy  this  defect  and  obtain  the  largest  percentage  of 
free  space  between  the  piers  for  the  passage  of  flood  waters, 
some  of  the  more  modern  Indian  works  have  been  given  much 
larger  openings  between  piers,  and  the  gates  are  so  operated 
that  no  superstructure  is  necessary  above  the  level  of  the  weir 
crest.  As  a  result  the  floods  may  pass  with  little  obstruction 


MA  HA  N  UDD  Y   SL  UICE   SHU  T  TERS.  1 3  7 

over  as  well  as  through  the  weirs.  Such  structures  as  these 
are  of  necessity  strongly  constructed  and  are  made  capable  of 
quick  operation.  Two  excellent  examples  of  this  class  of 
structure  are  furnished  by  the  shutters  in  the  Mahanuddy  weir 
at  the  head  of  the  Orissa  canals  and  those  of  the  Dehree  weir 
at  the  head  of  the  Soane  canals  in  India. 

153.  Mahanuddy  Sluice  Shutters. — These  shutters  are 
designed  somewhat  after  the  plan  adopted  on  some  of  the 
older  weirs  across  the  river  Seine  in  France.  The  sluiceway 
consists  of  ten  bays  each  50  feet  wide  and  separated  by  masonry 
piers.  Each  bay  is  closed  by  a  double  row  of  timber  shut- 
ters fastened  by  wrought-iron  bolts  and  hinges  to  a  heavy  beam 
of  timber  embedded  in  the  masonry  floor  of  the  sluice  (Fig. 


FIG.  33. — CROSS-SECTION  OF  MAHANUDDY  AUTOMATIC  SHUTTERS,  INDIA. 

33).  These  shutters  are  arranged  in  pairs  so  that  there  are 
seven  up-stream  and  seven  down-stream  shutters  in  each  bay. 
The  lower  shutters  are  9  feet  in  height  above  the  floor,  and 
the  upper  shutters  ;£  feet  in  height.  Each  bay  is  separated 
from  the  next  by  a  stone  pier  5  feet  thick,  to  which  the  gear- 
ing for  working  them  is  attached.  During  the  floods  the  up- 
per row  of  shutters,  which  fall  forward  up-stream,  are  held  to 
the  floor  of  the  weir  in  an  almost  horizontal  position  by  means 
of  iron  clutches.  The  rear  or  lower  row  of  shutters  which 
fall  down-stream  are  kept  in  a  horizontal  position  by  the  rush  of 
water  over  them.  In  order  that  the  down-stream  row  of  shut- 
ters may  be  retained  in  position  and  act  as  dams  when  raised, 
they  are  provided  with  strong  wrought-iron  struts  attached  to 


138      SCOURING   SLUICES,  REGULATORS,  AND  ESCAPES. 

their  lower  sides.  Iw  order  to  lift  the  lower  set  of  shutters 
when  the  water  is  resting  on  top  of  them  the  up-stream  set  of 
are  first  raised,  this  operation  being  aided  by  the  upward 
pressure  of  water  from  beneath,  and  they  are  retained  in  a 
vertical  position  by  means  of  chains  guyed  to  the  piers  above 
them.  Relieved  of  the  water  pressure  by  this  upper  set  of 
shutters,  it  then  becomes  possible  to  raise  the  lower  set  by 
means  of  a  hand  windlass,  after  which  the  upper  set  are  lowered 
again  into  their  original  position  and  the  weir  is  ready  to  with- 
stand the  next  flood,  as  the  lower  set  can  then  be  instantly 
dropped  by  merely  removing  the  bolts  which  support  them. 

154.  Soane  Automatic  Sluice  Gates. — The  shutters  of 
the  Mahanuddy  weir  have  never  been  successfully  operated 
against  a  greater  head  than  6J-  feet,  and  the  jar  produced  by 
opening  the  upper  gates  and  by  the  fall  of  the  lower  gates 
has  always  been  very  violent.  In  order  to  diminish  this 
jarring  action  and  to  obtain  a  more  easy  and  successful  opera- 
tion in  the  shutters  of  the  Soane  weir,  a  new  design  was  de- 
vised, and  it  furnishes  what  is  probably  the  best  example  of 
self-acting  sluice  gate  which  has  yet  been  constructed. 

The  crest  of  the  Soane  weir  is  9^-  feet  above  the  river-bed, 
and  the  gates  by  which  the  sluice  ways  are  closed  are  each  20 
feet  in  length  and  9^  feet  high.  They  are  separated  by  masonry 
piers  6J  feet  thick  by  32  feet  in  length.  The  floor  of  these 
sluices  is  very  substantial  and  is  90  feet  in  length  parallel  to 
the  river  channel.  As  the  velocity  of  the  current  through  them 
may  be  as  high  as  17^  feet  per  second,  it  was  found  necessary 
in  order  to  withstand  its  erosive  action  to  found  the  flooring 
on  wells  or  blocks  upon  which  an  ashlar  pavement  1 5  inches  in 
thickness  has  been  built  up.  The  gates  are  constructed  of  wood 
well  braced  and  set  in  pairs  in  each  opening  (PI.  VI.).  A  low 
masonry  wall  12  inches  high  has  been  built  upon  the  down- 
stream side  of  the  flooring  in  each  alternate  bay,  thus  giving  a 
water-cushion  of  that  depth  on  which  the  lower  gate  falls, 
relieving  the  piers  of  a  portion  of  the  shock.  The  upper  gate 
falls  up-stream,  being  hinged  to  the  floor  at  its  bottom  and 
held  upright  by  a  series  of  six  struts.  These  are  hollow  iron 


SOANE   AUTOMATIC   SLUICE   GATES,  139 

cylinders  with  small  ventholes,  and  in  them  pistons  work  in 
such  manner  that  when  the  gate  is  raised  by  the  pressure  of 
water  beneath  it  the  impact  against  the  struts  is  relieved  by  the 
pistons  plunging  into  the  cylinders,  from  which  the  water  is 
slowly  forced  through  the  vent  holes.  The  lower  gates  fall 
down-stream  and  are  supported  by  four  iron  rods  hinged  to 
their  upper  faces  below  the  centre  of  gravity,  and  when  in 
position  are  held  upright  by  chains  attached  to  the  piers  above. 
If  both  gates  are  open  and  it  is  desired  to  close  the  lower  one 
so  as  to  cause  it  to  dam  up  the  water,  it  is  first  relieved  by 
pushing  aside  the  catch  which  attaches  the  upper  gate  to  the 
floor  when  this  is  raised  a  little  by  means  of  a  hand  lever,  after 
which  the  force  of  the  water  brings  it  up  slowly  for  a  short 
distance  and  then  with  a  jar  against  its  hydraulic  struts  or 
rams.  The  pressure  is  now  relieved  from  the  lower  gates- 
which  can  be  raised  by  hand  levers  and  chained  in  an  upright 
position  to  the  piers.  The  upper  gate  is  again  lowered,  now 
falling  chiefly  by  its  own  weight  through  the  water,  and  is 
fastened  down  by  clutches.  The  lower  gate,  which  now  acts 
as  the  dam,  is  prepared  to  be  released  at  a  moment's  notice. 

155.  Relation  of  Weirs  to  Regulators. — A  diversion 
weir  retards  the  flow  of  the  stream  and  raises  the  level  of  the 
water  to  a  sufficient  height  to  enable  it  to  enter  the  canal 
head.  The  regulator  is  the  controlling  valve  which  admits 
this  water  to  the  canal  if  required,  or  prevents  its  entrance  and 
causes  it  to  pass  on  down  the  stream  over  or  through  the  weir. 
The  weir  is  the  boiler  which  generates  the  power ;  the  regu- 
lator is  the  throttle-valve  which  controls  its  entrance  to  the 
machinery.  The  regulator  should  be  so  located  with  relation 
to  the  weir  that  the  water  held  up  by  the  latter  will  pass  at 
once  and  with  the  least  loss  of  head  through  the  former  and 
into  the  canal.  This  is  effected  most  successfully  by  placing 
the  canal  head  immediately  adjacent  to  the  weir  and  building 
it  in  unison  with  and  as  part  of  the  structure.  The  weir  should 
not  be  so  aligned  as  to  cross  the  river  diagonally  at  an  angle 
inclined  either  to  or  from  the  regulator  head.  In  the  former 
case  it  tends  to  force  the  water  against  the  regulator,  creating 


140       SCOURING   SLUICES,  REGULATORS,  AND  ESCAPES. 


RELATION  OF    WEIRS    TO  REGULATORS.  14! 

an  unnecessary  scour  at  that  point  and  producing  an  undue 
pressure  or  strain  upon  the  head.  It  should  not  incline  away 
from  the  regulator,  as  the  reverse  effect  would  be  produced 
and  it  would  cease  to  perform  its  function  of  directing  the 
water  into  the  canal.  The  best  alignment  for  the  weir  with  re- 
lation to  the  regulator  is  to  have  it  cross  the  stream  at  right 
angles  to  the  line  of  the  weir.  This  gives  a  clear  even  scour 
past  the  regulating  gates  and  keeps  them  clear  of  silt,  at  the 
same  time  furnishing  the  required  amount  of  water. 

The  regulator  should  not  be  located  at  a  distance  from  the 
end  of  the  weir ;  otherwise  a  dead  water  is  created  between 
the  weir  and  the  regulator  in  which  deposits  of  silt  occur, 
blocking  the  entrance  to  the  canal  and  diminishing  the  volume 
available  for  its  supply.  An  excellent  example  of  such  faulty 
location  is  that  illustrated  in  Fig.  34,  showing  the  head  of  the 
Ganges  canal,  where  the  front  of  the  regulator  is  not  at  right 
angles  to  the  weir  and  is  at  a  short  distance  from  it,  resulting 
in  the  formation  of  a  sand-bar  at  its  entrance.  A  better 
arrangement  would  be  a  regulator  built  as  indicated  by  the 
dotted  outlines,  with  its  face  at  right  angles  to  the  line  of  the 
weir.  Another  example  of  the  improper  relation  of  weir  to 
regulator  is  that  at  the  head  of  the  Del  Norte  canal  in  Colorado, 
where  the  two  structures  make  an  angle  with  each  other, 
besides  being  separated  a  short  distance.  The  result  is  the 
formation  of  a  sand-bar  in  front  of  the  regulator  and  a  cor- 
responding diminution  in  the  supply  to  the  canal.  In  Egypt 
at  the  head  of  the  Ibrahmia,  Bahr  Yusef,  and  other  canals 
heading  in  a  common  basin  of  some  magnitude,  a  considerable 
deposit  of  Nile  mud  has  occurred  owing  to  the  slack  water 
created  in  front  of  the  canal  heads. 

A  good  example  of  the  proper  location  of  the  regulator 
and  weir  with  relation  to  each  other  are  furnished  by  the  head 
of  the  Agra  canal  in  India,  where  these  works  are  in  juxta- 
position to  and  at  right  angles  with  each  other,  resulting  in  a 
clear  waterway  in  front  of  the  head  where  the  main  channel 
of  the  stream  is  maintained.  The  proper  location  of  regulator 
to  weir  is  well  illustrated  by  the  head  of  the  Monte  Vista 


142     SCOURING    SLUICES,  REGULATORS,    AND   ESCAPES. 

canal  in  Colorado,  where  these  two  structures  head  at  right 
angles  and  adjacent  to  each  other ;  the  result  being  complete 
freedom  from  deposit  of  sediment  in  front  of  the  regulating 
gates  and  a  clear  channel  past  their  entrance.  Fig.  35  shows 


FIG.  34. — PLAN  OF  HEADWORKS.     GANGES  CANAL,  INDIA. 

the  plan  of  the  old  and  new  Arizona  headworks.  The  first 
weir,  as  shown  by  the  full  lines,  was  built  at  an  angle  to  the 
channel  of  the  stream,  and  the  regulator  head  was  built  at 
an  angle  both  to  the  stream  channel  and  to  the  weir,  the 
result  being  to  force  a  great  pressure  of  water  against  the 


CLASSIFICATION  OF  REGULATORS.  143 

regulating  gates,  resulting  ultimately  in  their  destruction,  while 
the  deposition  of  sediment  between  the  gates  and  weir  was 
greatly  encouraged.  The  present  headvvorks,  indicated  by  the 
cross-lined  weirs  and  the  dotted  canal,  lines  offer  an  excellent 


FIG.  35 — ARIZONA  CANAL.     PLAN  OF  HEADWORKS. 

example  of  good  location,  the  weir  being  at  right  angles  to 
the  river  channel  and  the  regulator  at  right  angles  to  the  weir ; 
resulting  in  perfect  freedom  from  silt  deposit  and  perma- 
nency in  the  regimen  of  the  stream. 

The  proper  relative  location  of  these  two  works  has  been 
obtained  by  different  methods  in  other  cases.  Thus  at  the 
headworks  of  the  Idaho  canal  (Fig.  66)  the  stream  channel  is 
bordered  by  a  basalt  ledge  about  12  feet  in  height.  The  weir 
is  constructed  between  the  walls  of  this  ledge  and  at  right 
angles  to  the  stream  channel.  The  regulating  head  is  placed 
on  top  of  the  ledge  with  a  scouring  sluice  in  the  weir  im- 
mediately in  front  of  and  below  it.  The  result  is  that  no  silt 
is  deposited  in  front  of  the  regulator  head,  though  this  is  not 
quite  at  right  angles  to  the  weir.  Any  sediment  which  may 
tend  to  settlement  at  this  point  falls  below  the  top  of  the 
basalt  ledge  and  is  carried  off  by  a  scouring  sluice. 

156.  Classification  of  Regulators. — The  type  of  regu- 
lator employed  depends  upon  the  character  of  the  foundation 


CO U RING   SLUICES,  REGULATORS,    AND   ESCAPES. 

and  the  permanency  which  is  deemed  desirable.  Regulators 
may  be  classified  according  to  the  design  of  the  gate  and  the 
method  by  which  it  is  operated.  With  nearly  any  type  of 
foundation  varying  degrees  of  permanency  may  be  given  the 
superstructure  and  various  methods  may  be  employed  for 
operating  the  gates.  Accordingly  regulators  are  classified 
here  as  follows  :  first,  wooden  gates  in  timber  framing  ;  second, 
wooden  gates  in  masonry  and  iron  framing ;  third,  iron  gates 
in  masonry  and  iron  framing.  They  are  further  classified 
according  to  the  method  of  operating  the  gates  as  follows : 
first,  flashboard  gates ;  second,  gates  raised  by  hand  lever ; 
third,  gates  raised  by  chain  and  windlass ;  fourth,  gates  raised 
by  screw  gearing. 

Simple  flashboard  or  needle  gates  can  only  be  used  where 
the  pressure  upon  them  is  low.  When  under  great  pressure 
the  opening  should  generally  be  closed  by  a  simple  sliding 
gate  which  may  be  raised  by  hand  lever  or  windlass.  Where 
under  considerable  pressure,  a  double  series  of  gates  one 
above  the  other,  each  separately  raised  by  a  lever  or  windlass, 
may  be  employed,  and  these  should  be  operated  by  a  screw 
and  hand  gear  from  above. 

157.  General  Form  of  Regulator. — The  regulator  should 
be  so  constructed  that  the  amount  of  water  admitted  to  the' 
canal  can  be  easily  controlled  at  any  stage  of  the  stream. 
This  can  only  be  done  by  having  gates  of  such  dimensions 
that  they  can  be  quickly  opened  or  closed  as  desired.  Accord- 
ingly, when  the  canal  is  large  and  its  width  great  the  regulator 
should  be  divided  into  several  openings,  each  closed  by  a 
separate  and  independent  gate.  The  width  of  these  openings 
should  be  rarely  less  than  2  feet  nor  more  than  6  feet.  The 
channel  of  the  regulator  way  should  consist  of  a  flooring  of 
timber  or  masonry  to  protect  the  bottom  against  the  erosive 
action  of  the  water,  and  of  side  walls  or  wings  of  similar 
material  to  protect  the  banks.  The  various  openings  will  be 
separated  by  piers  of  wood,  iron,  or  masonry,  and  the  amount 
of  obstruction  which  they  offer  to  the  channel  should  be  a 
minimum,  in  order  that  the  width  of  the  regulator  head  shall 


ARRANGEMENT   OF   CANAL   HEAD.  14$ 

be  as  small  as  possible  for  the  desired  amount  of  opening. 
For  convenience  in  operation  it  is  customary  to  surmount  the 
regulator  by  arches  of  masonry  or  a  flooring  of  wood,  so  as  to 
give  an  overhead  bridge  from  which  the  gates  may  be  handled. 
Lastly,  the  height  of  the  regulating  gates  and  the  height  of  the 
bridge  surmounting  them  must  exceed  the  height  of  the  weir 
crest  by  the  amount  of  the  greatest  afflux  height  which  the 
floods  may  attain,  in  order  that  these  shall  not  top  the  regu- 
lator and  destroy  the  canal.  The  regulator  must  be  firmly 
and  substantially  constructed  to  withstand  the  pressure  of 
great  floods,  and  a  drift  fender  should  be  built  immediately  in 
front  of  or  at  a  little  distance  in  advance  of  the  gates.  Wooden 
regulator  heads  are  usually  constructed  much  as  are  open 
flumes,  and  consist  of  a  fluming  or  boxing  of  timber  lined  with 
planks  on  the  bottom  and  sides  and  with  cross  bracing  above. 
In  this  are  set  the  piers  and  gates. 

158.  Arrangement  of  Canal  Head. — As  already  shown, 
the  regulator  gates  should  be  as  close  as  possible  to  the  end  of 
the  weir  in  order  to  prevent  the  deposit  of  silt  at  this  point. 
Owing  to  the  character  of  the  banks  and  to  avoid  excessive 
cost  in  first  construction,  it  is  sometimes  found  necessary  to  set 
the  regulator  back  in  the  canal  a  short  distance.  In  such  cases 
an  escape  should  be  introduced  in  front  of  and  adjacent  to  it 
to  relieve  it  of  pressure  and  aid  in  its  effective  operation. 

At  the  head  of  the  Cavour  canal,  Italy,  the  regulator  is  set 
back  in  the  head  cut,  and  immediately  in  front  of  it  is  placed 
an  escape  discharging  into  the  river.  At  the  head  of  the  Tur- 
lock  canal  in  California  the  flood  heights  are  so  great  that  the 
water  may  rise  above  the  weir  crest  to  a  height  of  16  feet.  In 
order  to  relieve  the  gates  of  this  pressure  the  canal  heads  di 
rectly  in  a  tunnel  which  is  560  feet  in  length  and  12  feet  wide 
at  the  bottom  and  is  cut  through  the  solid  rock.  It  discharges 
into  an  open  rock  cut  across  which  is  placed  the  regulator, 
while  immediately  above  it  and  at  right  angles  to  it  are  a 
series  of  escape  gates  discharging  back  into  the  river.  The 
wasting  capacity  of  this  escape  is  made  greater  than  the  possi- 


146     SCOURING  SLUICES,  REGULATORS,    AND  ESCAPES. 

ble  discharge  of  the  tunnel  under  the  greatest  head  of  water,  so 
that  the  regulator  gates  are  relieved  of  most  of  the  pressure. 

At  the  head  of  the  Pecos  canal  in  New  Mexico,  the  regulator 
gates  are  set  back  in  a  deep  rock  cut  some  distance  from  the 
entrance.  This  cut  is  850  feet  in  length,  and  at  its  lower  end 
between  the  abutment  of  the  weir  and  adjacent  to  the  regulat- 
ing gates  is  an  escape-way  discharging  into  the  river.  By  this 
means  a  clear  scour  can  be  maintained  past  the  gates  and  the 
deposit  of  silt  prevented,  while  at  the  same  time  the  pressure  is 
reduced.  At  the  head  of  the  Central  Irrigation  District  canal 
there  is  no  weir,  as  the  discharge  of  the  Sacramento  river  is 
always  more  than  sufficient  to  fill  the  canal,  the  bed  of  which 
is  from  I  to  2  feet  below  low-water  level.  The  regulator  at 
the  head  of  the  canal  consists  of  two  parts,  a  main  set  of  ma- 
sonry headgates  set  back  in  the  cut  one  third  of  a  mile  from 
the  river  banks,  and  a  secondary  set  of  regulating  gates  and  a 
waste  gate  placed  three  miles  further  back  in  the  cut.  There 
is  no  pressure  to  be  withstood  by  the  first  set  of  masonry 
gates,  since  the  water  is  held  up  by  the  second  set  in  such 
manner  as  to  equalize  the  pressure  on  both  sides  of  the  first 
set  of  gates  and  thus  permit  them  to  be  raised  by  a  simple 
contrivance. 

159.  Wooden   Flashboard    Regulators. — Simple    flash- 
board  regulators  are  constructed  as  are  flashboard  weirs.     A 
satisfactory  regulator  of  this  kind  is  that  at  the  head  of  the 
Galloway  canal  in  California,  which  is  almost  identical  in  con- 
struction with  the  weir  (Fig.  17)  and  therefore  scarcely  requires 
description.     It  consists  of  a  wooden   fluming  having  a  rect- 
angular cross-section  built  into  the  canal  head  and  resting  on 
piles  and  protected  by  sheet  piling.     Above  and  below  this 
regulator  head  are  built  a  wooden  flooring  and  wings  to  pre- 
vent erosion.     Flashboards  are  laid  in  the  regulator  head  and 
can  be  removed  or  replaced  one  at  a  time,  according  to  the 
amount  of  water  to  be  admitted. 

160.  Wooden  Regulator  Gate  lifted  by   Lever.— This 
form  of  regulator  consists  of  a  rectangular  fluming  similar  to 
that  just  described,  which  generally  extends  from  8  to  10  feet 


WOODEN   GATE  LIFTED   BY    WINDLASS. 


up-stream  from  the  gates  and  15  or  20  feet  below  them. 
Sometimes,  instead  of  the  flooring  being  horizontal  and  hav- 
ing sheet  piling  at  its  termini  to  prevent  seepage,  its  ends  are 
carried  down  at  an  angle  of  from  30  to  45  degrees  for  a  depth 
of  several  feet  into  the  river-bed.  As  shown  in  Fig.  36,  these 
simple  lifting  gates  consist  ordinarily  of  boards  laid  together 
horizontally  and  framed  or  braced  with  wood  or  iron  so  as  to 
make  a  firm  shutter  or  gate.  Above  this  extends  an  upright 
post  or  handle  with  holes  in  it,  into  which  the  point  of  a  hand 
lever  is  inserted  and  the  gate  can  be  thus  raised.  It  slides  ver- 
tically between  upright  timbers  and  is  held  in  position  when 
raised  by  the  insertion  of  an  iron  plug  into  the  lever  holes. 
This  type  of  gate  is  used  on  the  Cavour  canal  in  Italy  and  on 
tKe  Arizona,  Merced,  and  many  other  canals  in  this  country. 

161.  Wooden  Gate  lifted  by  Windlass. — One  of  the 
most  notable  examples  of  this  type  of  gate  is  that  at  the  head 
of  the  Ganges  canal  in  India,  the  regulator  of  which  is  of 
masonry,  the  gates  being  separated  by  masonry  piers.  The  head 
on  the  gates  is  such  that  it  is  necessary  to  have  three  tiers  of 
gates  one  above  the  other,  the  most  advanced  or  up-stream 
gate  having  its  sill  on  a  level  with  the  canal-bed  and  the  two 
higher  gates  having  their  sills  each  6  feet  higher,  while  they 


FIG.  36.— REGULATOR  GATES,  GANGES  CANAL. 


retrograde  toward  the  face  of  the  bridge  by  the  width  of  a 
gate.  On  the  bridge  above  are  two  simple  horizontal  wooden 
windlasses,  and  the  gates  are  raised  by  turning  these. 


SCOURING   SLUICES,  REGULATORS,   AND   ESCAPES. 


162.  Gate  lifted  by  Travelling  Winch.  —  This  is  the  most 
common  form  of  gate  employed  in  India  where  the  width  of 
canal  head  is  great  and  the  number  of  openings  correspond- 
ingly large.  As  before  stated,  the  regulator  heads  there  are 
invariably  built  of  masonry,  each  opening  being  separated  by 
masonry  pillars.  As  shown  in  Fig.  37,  the  gate  is  constructed 


Loner  a  net  u/opir  UppV   jot*   yicn  Both    fates  ctaita 

Get*  fvU  <?£&>. \ 

FIG.  37. — REGULATOR  GATES,  SOANE  CANAL. 

of  wood,  cross-braced,  and  to  its  top  are  attached  chains  which 
run  over  the  windlass  of  the  travelling  winch.  Above  these 
gates  is  a  bridge,  and  on  the  parapet  immediately  over  the 
gates  is  a  simple  railroad  track  on  which  a  handcar  is  run.  On 
this  is  placed  a  simple  hand  winch,  and  by  turning  this  each 
gate  can  be  successively  raised  or  lowered  and  the  winch 
pushed  along  to  the  next  gate. 

163.  Gate  raised  by  Gearing  or  Screw. — This  type  of 
gate  is  common  both  in  this  country  and  abroad.  They  are  gen- 
erally employed  where  there  is  pressure  to  be  overcome  and  are 
slow  in  their  operation.  As  a  consequence  a  few  simple  lifting 
gates  are  generally  inserted  in  a  few  of  the  openings,  to  be 
used  when  the  pressure  is  light,  and  a  few  geared  gates  are 
employed  to  be  operated  under  pressure.  Such  a  gate  is  that 
at  the  head  of  the  Arizona  canal  (Fig.  38),  which  is  constructed 


GATE  RAISED  BY  GEARING  OR   SCREW. 


149 


of  wood  framed  with  iron.     Above  it  projects  a  heavy  steel 
screw,  i£  inches  in  diameter,  and  this  passes  through  a  female 


FIG.  38. — REGULATOR  GATES,  ARIZONA  CANAL. 

screw  of  malleable  iron  on  which  the  wear  is  taken  up.     As 
the  pressure  which  this  gate  has   to  withstand  is  great,  the 


FIG.  39.— REGULATOR  GATES,  DEL  NORTE  CANAL. 

simple  screw  is  not  sufficient,  and  the  female  screw  forms  the 
inner  surface  or  axis  of  a  geared  or  cogged  wheel,  and  this  is 


I5O  SCOURING   SLUICES,  REGULATORS,    AND  ESCAPES. 


Scale 


i      i      i      i      i      i      i 

~ 


i&     4       "  — ^g.,,    .     _>.  .  ,.   21'     2  Ji  ^ 

PLATE  VII.    BEAR  RIVER  CANAL.    ELEVATION  AND  CROSS-SECTION  OF  WEIR  AND  REGULATORJJ 


ROLLING  REGULATOR   GATE. 


turned  by  a  smaller  cog  operated  by  a  hand  wheel ;  thus  the 
gate,  while  moving  very  slowly,  can  be  raised  with  the  appli- 
cation of  but  a  trifling  amount  of  power,  owing  to  the  multi- 
plicity of  gearing  employed. 

A  simpler  gate  of  the  same  general  type  is  that  at  the  head 
of  the  Del  Norte  canal  in  Colorado.  As  shown  in  Fig.  39,  the 
lifting  screw  is  attached  to  the  gate  and  turns  in  a  female  screw 
attached  to  the  overhead  bridge. 

A  more  substantial  gate  is  that  at  the  head  of  the  Bear  River 
canal  in  Utah,  which  is  set  between  firm  masonry  abutments 
and  slides  in  an  iron  frame.  This  gate  is  of  iron  and  to  it  is 
attached  an  upright  screw  which  works  in  a  female  screw  the 
outer  circumference  of  which  is  cogged,  and  is  turned  by  an 


FIG.  40.-—  -SLIDING  REGULATOR  GATE,  IDAHO  CANAL, 

endless  wheel  operated  by  a  hand  lever  (PL  VII).  An  ingenious 
method  of  operating  gates  is  that  employed  on  the  Idaho 
Mining  Company's  canal  at  the  head  of  the  escapes  and 
smaller  regulators.  To  the  upper  part  of  the  gate  are  attached 
two  uprights  (Fig.  40)  on  which  are  plain  iron  cogged  racks. 
On  these  work  cogged  pinions  turned  by  hand  levers,  which 
cause  the  gates  to  move  up  and  down. 

164.  Rolling  Regulator  Gate.— This  form  of  gate  (Fig.  41) 
is  employed  at  the  head  of  the  Idaho  Mining  Company's  canal, 
and  is  similar  to  that  employed  on  the  open  weirs  on  the  river 
Seine  in  France  (Fig.  20).  The  regulator  consists  of  eight  open- 
ings, each  8  feet  wide  and  19  feet  high,  and  is  constructed  of 
substantial  masonry,  surmounted  by  a  bridge  the  height  of 
which  is  21  feet  above  the  canal  bed.  The  gates  which  close 
the  openings  are  separated  by  masonry  piers  3  feet  in  thickness, 


152      SCOURING  SLUICES,  REGULATORS,   AND  ESCAPES, 


HYDRAULIC  LIFTING   GATE. 


153 


and  consist  of  roller  curtains  made  of  steel  plates  and  angle 
iron  to  a  height  of  10  feet  from  the  bottom,  above  which  the 
curtain  is  constructed  of  pine  slats,  each  6  inches  wide.  There 
are  20  steel  slats  and  8  of  wood,  and  the  bottom  of  the  curtain 


FIG.  41.— ROLLING  REGULATOR  GATE,  IDAHO  CANAL. 

is  fastened  to  a  cast-iron  roller,  on  which  it  is  wound  up  from 
above,  in  the  form  of  a  spiral,  by  means  of  a  chain  operated 
from  the  overhead  bridge  by  a  winch. 

165.  Hydraulic  Lifting  Gate. — At  the  head  of  the  Folsom 
canal  in  California  the  regulating  gates  (PL  XXVII)  are  oper- 
ated by  hydraulic  power  from  an  accumulator  fed  by  water 


154      SCOURING   SLUICES,  REGULATORS,    AND   ESCAPES. 

power  from  a  fall  in  the  canal.  This  regulator  is  constructed 
in  the  most  substantial  manner  of  granite  masonry,  and  has  a 
total  width  of  66  feet  between  the  abutments.  The  gates  (PL 
VIII)  are  three  in  number,  each  16  feet  in  width  and  14  feet  in 
height  to  the  crest  of  a  semi-circular  arch,  and  are  separated 
by  masonry  piers  6  feet  in  thickness.  They  are  of  wood,  well 
braced,  and  slide  vertically  in  grooves  let  into  the  masonry 
piers  separating  them.  One  hydraulic  jack  is  attached  to  each 
gate,  and  its  cylinder  is  fastened  to  the  masonry  above.  In 
this  works  a  steel  plunger  having  a  14-foot  stroke  and  directly 
connected  at  its  lower  end  with  the  gate. 

166.  Escapes. — In  order  to  establish  a  complete  control 
over  the  water  in  a  canal  channel,  provisions  should  be  made 
for  disposing  of  any  excess  which  may  arise  from  sudden 
rains  or  floods  or  from  water  not  required  for  irrigation. 
This  is  effected  by  means  of  escapes,  or,  as  they  are  more  com- 
monly called  in  this  country,  wasteways.  These  are  short  cuts 
from  the  canal  to  some  natural  drainage  way  into  which  the 
excess  of  water  can  be  discharged.  Escapes  perform  the  addi- 
tional service  of  flushing  the  canal  and  thus  preventing  or 
scouring  out  silt  deposits. 

If  the  heads  of  distributaries  be  opend  they  relieve  the 
main  canal,  and  the  former  are  in  turn  relieved  by  opening  the 
escapes ;  hence  the  distributary  heads  act  as  the  safety-valves 
and  the  escapes  as  the  waste-pipes  of  a  canal  system.  Escapes 
should  be  provided  at  intervals  along  the  entire  canal  line,  the 
lengths  of  the  intervals  depending  on  the  topography  of  the 
surrounding  country,  the  danger  from  floods  or  inlet  drainage, 
and  the  dimensions  of  the  canal.  On  large  canal  systems  in 
India  it  is  customary  to  place  them  at  intervals  from  20  to  40 
miles.  In  our  own  country  they  are  placed  more  frequently, 
usually  10  to  20  miles  apart.  Where  the  regulator  head  is 
placed  back  from  the  river  a  short  distance,  as  in  the  case  of 
the  Cavour,  Pecos,  and  Turlock  canals,  an  escape  should  be 
provided  immediately  above  the  regulator  head  for  the  dis- 
charge of  surplus  water  and  in  order  that  the  channel  may  be 
kept  free  from  silt.  The  first  or  main  escape  on  the  canal 


LOCATION  AND    CHARACTERISTICS  OF  ESCAPES.        155 

line  should  always  be  constructed  at  a  distance  not  greater 
than  half  a  mile  from  the  regulator,  in  order  that  in  case  of 
accident  to  the  canal  the  water  may  immediately  be  drawn  off. 
This  main  escape  has  the  additional  advantage  of  acting  as  a 
flushing  gate  for  the  prevention  and  removal  of  silt  deposits. 
Where  used  for  the  latter  purpose  it  is  customary  to  decrease 
the  slope  of  the  canal  between  its  head  and  the  escape,  in  order 
that  the  matter  carried  in  suspension  may  be  deposited  at  that 
point. 

167.  Location  and  Characteristics  of  Escapes. — Escapes 
should  be  located  above  weak  points,  as  embankments,  flumes, 
etc.,  in  order  that  the  canal  may  be  quickly  emptied  in  case 
of  accident.  Their  position  should  be  so  chosen  that  the 
escape  channels  through  which  they  discharge  shall  be  of  the 
shortest  possible  length.  These  must  have  sufficient  discharge 
to  carry  off  the  whole  body  of  water  which  may  reach  them 
from  both  directions,  so  that  if  necessary  the  canal  below  the 
escape  may  be  laid  bare  for  repairs  while  it  is  still  in  opera- 
tion above. 

The  greatest  danger  from  injury  to  canals  is  during  local 
rains,  when  the  irrigator  ceases  to  use  the  water,  thus  leaving 
the  canal  supply  full,  while  its  discharge  is  augmented  by  the 
flood  waters.  Hence  it  is  essential  where  a  drainage  inlet 
enters  the  canal  that  an  escape  be  placed  opposite  it  for  the 
discharge  of  surplus  water.  During  floods  the  escape  acts  in 
relieving  the  canal  of  surplus  water  as  though  the  head  regu- 
lator of  the  canal  had  been  brought  so  much  nearer  the  point 
of  application.  In  order  that  the  escape  way  may  act  most 
effectively  the  slope  of  its  bed  should  be  increased  by  at  least 
12  inches  immediately  below  its  head;  in  addition  to  which 
the  slope  of  the  remainder  of  the  bed  should  be  a  little  greater 
than  that  of  the  canal,  and  it  should  tail  into  the  drainage 
channel  with  a  drop  of  a  few  feet.  It  is  common  in  this 
country  to  build  escapes  in  the  sides  of  flumes,  thus  taking 
advantage  of  the  wooden  construction  as  an  escape  head  and 
avoiding  the  expense  of  constructing  an  escape  cut,  as  the 
water  is  discharged  immediately  into  the  drainage  channel  be- 


SCOURING    SLUICES,  REGULATORS,    AND   ESCAPES. 

neath  the  flume.  While  this  practice  is  economical  and  may 
serve  well  where  cheap  construction  is  necessary,  it  is  far  from 
the  best  method  unless  great  care  is  taken.  The  water  falling 
from  the  flume  may  damage  its  foundations  while  the  escape 
does  not  add  to  the  security  of  the  structure  in  which  it  is 
placed,  as  it  does  not  shut  off  the  water  above  it. 

168.  Design  of  Escape  Heads.— Escape  heads  and  the 
regulators  placed  in  the  canal  adjacent  to  and  below  them  are 
built  on  similar  designs  to  the  main  regulating  gates  at  the 
head  of  the  canal.  A  maximum  limit  is  given  to  the  dimen- 
sions of  each  gate,  and  as  many  are  inserted  as  are  necessary 
to  pass  the  entire  discharge  of  the  canal  without  obstructing 
its  velocity.  These  gates  may  be  of  wood  or  iron,  and  may 
be  framed  between  timber,  iron,  or  masonry  piers  and  abut- 
ments. They  are  operated  as  are  the  head  regulating  gates; 
but  as  the  pressure  on  them  is  never  great,  some  simple  form 
of  lifting  apparatus,  as  flashboards  or  sliding  gates  raised  by 
hand  lever,  windlass,  or  simple  screw,  is  sufficiently  effective. 

On  the  Galloway  canal  in  California  wooden  flashboard 
escape  gates  are  used  which  are  similar  to  the  Galloway  falls 
and  regulating  gates  (Fig.  17).  The  escapes  on  the  Idaho  canal 
consist  of  cylindrical  pipes  let  through  the  banks,  the  entrance 
to  each  being  closed  by  a  sliding  gate  raised  by  rack  and  pinion 
(Fig.  40).  On  the  Highline  canal  in  Colorado  the  first  main 
escape  is  in  the  bench  flume  600  feet  below  the  head  regulator, 
and  consists  of  a  set  of  four  wooden  gates,  each  3  by  4  feet,  set 
into  the  side  of  the  flume  and  raised  by  simple  rack  and  pinion. 
In  the  flume  below  and  adjacent  to  this  escape  head  are  a  set  of 
flashboard  checks  for  regulating  the  discharge  of  the  canal,  or, 
if  necessary,  of  closing  it  and  forcing  all  the  water  through  the 
escape.  In  addition  to  this  there  are  several  other  escapes 
along  the  line  of  the  canal,  a  few  at  drainage  inlets,  and  one  in 
each  of  the  important  flumes  on  the  line.  For  complete  con- 
trol of  the  water  on  the  Bear  river  canal  there  are  two  head 
escapes,  one  1200  feet  and  the  other  1800  feet  below  the  head 
regulating  gates,  and  discharging  back  over  the  canyon  sides 
into  the  river.  Each  of  these  escapes  has  12  feet  of  clear  open- 


DESIGN  OF  ESCAPE  HEADS.  1 57 

ing  closed  by  three  wooden  gates  sliding  between  iron  posts 
and  raised  by  screw  gearing.  Below  and  adjacent  to  the  lower 
escape  is  a  set  of  regulating  gates  in  the  canal. 

On  the  line  of  the  Turlock  canal  abundant  escape  way  has 
been  provided,  as  the  canal  flows  in  natural  drainage  channels 
for  a  portion  of  its  course.  One  of  these,  Dry  creek,  has  a 
large  catchment  basin,  and  the  diverting  dam  which  turns  the 
water  back  into  the  canal  is  provided  with  an  escape  weir  51 
feet  in  length,  besides  an  escape  way  30  feet  in  length.  An 
interesting  escape  on  the  line  of  this  canal,  however,  is  that  at 
the  bottom  of  the  flume  crossing  Peasley  creek.  This  flume 
is  20  feet  wide  and  7  feet  deep  and  is  carried  on  a  trestle  60 
feet  in  height  above  the  stream  bed.  In  the  bottom  of  the 
flume  is  built  an  escape  which  is  of  sufficient  capacity  to  dis- 
charge the  full  volume  of  water  flowing  in  the  flume.  It  is 
built  by  laying  an  iron  beam  across  the  flume  bed,  and  this  re- 
volves on  an  axis  turned  by  means  of  a  hand  wheel,  thus  con- 
verting a  portion  of  the  floor  into  a  revolving  gate  by  opening 
the  bottom  of  the  flume  for  its  entire  width.  Beneath  this 
gate  is  a  receiving  box  which  discharges  up  and  down  stream 
into  two  inclined  wooden  flumes  which  lead  the  water  into 
the  creek. 

169.  Sand  Gates. — Sand  gates  are  practically  escape  gates, 
though  they  are  so  designed  and  arranged  in  some  canals  as 
to  be  of  service  only  in  scouring  or  removing  silt  deposits. 
The  main  or  head  escape  on  a  canal  system  acts  as  a  sand 
gate,  and  is  generally  built  as  much  for  the  purpose  of  flushing 
and  scouring  sediment  as  for  the  control  of  water  in  the  canal. 
The  gate  in  the  Highline  flume  acts  effectively  as  a  sand  gate, 
because  a  board  check  from  I  to  2  feet  in  height  is  placed 
across  the  flume  below  the  escape  head.  This  causes  the  de- 
posit of  silt  immediately  above  it,  whence  it  can  be  removed 
by  the  scour  through  the  escape. 

Careful  provision  has  been  made  for  the  removal  of  silt 
on  the  Folsom  canal.  Immediately  in  front  of  and  above  the 
regulating  head  is  a  set  of  four  sand  gates  placed  6  feet  below 
the  grade  of  the  canal  and  discharging  directly  back  into  the 


158      SCOURING   SLUICES,  REGULATORS,    AND   ESCAPES. 

river.  These  are  practically  undersluice  gates,  and  are  each 
5  by  6  feet  in  the  clear  and  set  in  substantial  masonry. 
Sediment  which  is  dropped  into  the  subgrade  in  the  canal 
opposite  these  gates  is  scoured  out  through  them.  In  addition 
to  these  sand  gates,  seven  others  are  placed  in  the  first  1700 
feet  of  the  canal.  These  are  all  similar  in  construction,  5  feet 
wide  by  10  feet  high,  framed  in  substantial  masonry,  and  consist 
of  iron  gates  sliding  vertically  and  raised  by  means  of  a  hand 
wheel  and  endless  screw  working  on  ratchets  set  on  the  back  of 
the  gate.  Across  the  bed  of  the  canal  opposite  and  below  each 
of  these  sand  gates  is  a  subchannel  and  catch-basin  I  foot  in 
depth,  the  object  of  which  is  to  collect  silt  which  is  afterwards 
scoured  out  through  the  gates. 


CHAPTER   XIV. 
FALLS   AND    DRAINAGE   WORKS. 

170.  Excessive  Slope. — As  the  natural  fall  of  the  country 
through  which  a  canal  runs  is  usually  greater  than  the  slope  of 
the  canal,  the  tendency  of  the  water  in  the  latter  is  to  erode  its 
bed.  In  a  small  section  of  the  line  the  erosive  action  of  the 
water  on  the  bed  is  noticeable  providing  the  velocity  of  the 
stream  be  great.  When  this  erosive  action  is  extended  to 
long  reaches  of  the  channel  it  produces  what  is  known  as  re- 
trogression of  levels,  which  is  the  direct  result  of  too  great  a 
slope  and  consequent  too  high  velocity.  If  the  canal  is  straight 
little  harm  is  done  by  this,  other  than  to  cause  the  level  of 
the  water  to  sink  below  the  ground  surface  and  prevent  its 
diversion.  Where  it  is  necessary  to  divert  the  water  or  where 
there  are  curves  which  the  increased  erosive  action  of  the  water 
would  injure,  it  becomes  necessary  to  compensate  for  the  dif- 
ference between  the  slope  of  the  country  and  the  canal-bed,  so 
as  to  reduce  the  velocity.  This  is  done  by  concentrating  the 
difference  of  slope  in  a  few  points  where  vertical  falls  or  rapids 
are  introduced.  The  location  of  these  is  usually  fixed  by  the 
place  where  the  canal  comes  too  high  above  the  surface  of  the 
ground,  while  their  distance  apart  is  so  arranged  that  they  shall 
not  have  an  excessive  height  or  fall.  If  a  canal  can  be  so  lo- 
cated and  aligned  that  it  will  skirt  the  slopes  of  the  country 
on  a  grade  contour,  it  becomes  possible  to  give  it  the  most  de- 
sirable slope  throughout  its  length  without  the  introduction  of 
falls ;  but  where  it  runs  down  the  slope  of  the  country,  compen- 
sation must  be  made  for  the  difference  between  the  excessive 
ground  slope  over  that  of  the  canal. 

159 


l6o  FALLS  AND   DRAINAGE    WORKS. 

171.  Falls  and  Rapids.— There  are  two  general  methods 
of  compensating  for  slope:  one  is  by  the  introduction  of  verti- 
cal drops  or  falls,  and  the  other  by  the  use  of  inclined  rapids 
or  chutes.     Falls  and  rapids  are  of  various  kinds  and  may  be 
generally  classified  according  as  they  are  of  wood  or  masonry. 
In  design  the  fall  maybe  of  three  general  types:  I,  it  may 
have  a  clear  vertical  drop  to  a  wooden  or  masonry  apron ;  2, 
the  lower  face  of  the  fall  may  be  given 'an  ogee-shaped  curve 
(Article  137)  with  the  object  of  diminishing  the  velocity  and 
consequent  erosive  action    of   the  water;    3,  the    water   may 
plunge  into  a  water-cushion  (Article   138).      To  prevent  the 
scour  above  the  fall  induced  by  the  increased  velocity  of  ap- 
proach ;   i,  a  flashboard  weir  may  be  erected  at  the  crest ;  2,  the 
channel  may  be  contracted,  or  3,  gratings  may  be  introduced. 
To  prevent  the  erosive  action  in  the  lower  level  at  the  foot  of 
the  fall  a  water-cushion  may  be  employed,  or  the  channel  may 
be  increased  in  width,  terminating  in  wings  which  shall  deflect 
the  eddies  back  against  the  fall. 

172.  Retarding  Velocity  by  Flashboards  on  Fall  Crest. 
— The  effect  of  a  fall  is  to  increase  the  velocity  and  to  diminish 
the  depth  of  water  for  some  distance  above  it.     This  increase 
of  velocity  produces  a  dangerous  scour  on  the  bed  and  banks 
of  the  canal,  which  in  a  properly  constructed  fall  is  guarded 
against  by  means  of  flashboards  or  by  narrowing  the  width  of 
the  channel.     The  height  to  which  it  is  necessary  to  raise  the 
crest  of  the  fall  is  found  by  the  following  formula  devised  by 
Colonel  Dyas  of  the  Indian  Engineers : 

r 
~  12S-8I227'      '    '    '    '    0) 

in  which  h  =  height  in  feet  of  the  water  surface  above  the  crest 

of  the  fall ; 
a  =  the  sectional  area  of  the  open  channel  in  square 

feet; 

r  =.  the  hydraulic  mean  depth  of  the  same  in  feet ; 
/  =  the  length  of  the  crest  of  the  fall  in  feet ; 
f=  the  length  of  slope  to  a  fall  of  one  in  the  same. 


RETARDING  VELOCITY  OF  APPROACH.  l6~I 

This  formula  has  been  somewhat  simplified  and  modified  by 
Mr.  P.  J.  Flynn  in  order  to  make  it  agree  with  Kutter's  formula. 
Mr.  Flynn  finds  the  discharge  over  the  fall  complete  to  be 


in  which  Q  =  the  discharge  in  second-feet  ; 

c  =  the  coefficient  of  discharge  of  open  channel  ; 
/;/  —  coefficient  of  discharge  over  a  weir,  and  varies 

between  2.5  and  3.5  ; 

s  =  the  sign  of  slope  ;  and  finally  he  gives  the  fol- 
lowing : 


If  from  this  value  of  //  we  deduct  the  depth  of  water  in  the 
channel,  we  have  the  height  to  which  the  weir  must  be  raised 
above  the  bed  of  the  canal  in  order  that  the  water  shall  not 
increase  in  velocity  in  approaching  the  crest  of  the  fall. 

173.  Retarding  Velocity  by  contracting  Channel.  —  If, 
instead  of  raising  the  crest  of  the  fall,  it  is  desired  to  narrow 
the  channel  above  the  fall  in  order  to  diminish  the  velocity  of 
approach  and  the  consequent  erosive  action,  the  amount  of 
narrowing  may  be  calculated  by  the  common  weir  formula 
(No.  2)  above  given,  and  substituting  for  Q  its  value  ac(rs}^, 
and  transposing  we  finally  get 


_  2agc  2grs_  } 

-^    <  (2g/i  +  Sr7)*' 

in  which  /  is  the  length  of  the  weir  crest  or  the  width  of  the 
channel  immediately  above  the  fall,  in  feet. 

174.  Gratings  to  retard  Velocity  of  Approach.—  Gratings 
have  not  been  employed  on  American  canals  for  the  purpose  of 
retarding  the  velocity  of  approach  to  the  crest  of  falls,  but  are 
used  with  excellent  results  on  some  canals  in  India.  They 


162 


FALLS  AND  DRAINAGE    WORKS. 


consist  of  a  number  of  inclined  wooden  bars  placed  just  above 
the  crest  of  the  fall,  and  the  method  of  spacing  them  is  such 
that  the  velocity  of  no  one  part  of  the  stream  shall  be  either 
increased  or  retarded  by  the  proximity  of  the  fall.  The  wooden 
bars  which  rest  on  one  or  more  overhead  cross-beams,  are  laid 
at  a  slope  of  about  I  on  3,  and  are  made  of  such  length  that  the 
full  supply  level  in  the  canal  is  half  a  foot  below  their  ends.  In 
canals  with  6J  feet  depth  of  water  the  following  dimensions 
have  been  used  for  the  bars :  lower  end  \  inch  broad  by  f  of  an 
inch  deep ;  upper  end  \  inch  broad  by  f  of  an  inch  deep.  They 
are  supported  on  12  X  12  inch  beams,  and  are  placed  such  dis- 
tance apart  that  18  go  into  one  lo-foot  bay. 

According  to  the  experience  had  in  India  vertical  falls  ter- 
minating in  a  water-cushion  and  having  gratings  above  them 
are  the  best  form  that  has  yet  been  devised,  the  erosive  action 
being  diminished  to  a  minimum. 

175.  Simple  Vertical  Fall  of  Wood.— On  the  line  of 
the  Galloway  canal  in  California  simple  flashboard  checks  sim- 
ilar to  the  regulating  heads  are  used  for  the  falls.  By  increas- 
ing or  diminishing  the  number  of  flashboards  inserted  in  these 


FIG.  42. — LONGITUDINAL  SECTION  OF  FALL,  ARIZONA  CANAL. 

checks  the  height  of  fall  can  be  increased  or  diminished  as 
desired.  These  checks  are  inclined  at  a  slight  angle  to  the 
vertical,  and  the  water  drops  to  a  wooden  apron  or  flooring 
resting  on  mudsills  and  protected  by  sheet  piling  at  its  ends, 


SIMPLE    "EKT1CAL  FALL   OF  WOOD. 


I63 


while  the  bank  is  protected  by  wings.  On  the  line  of  the 
Arizona  canal  (Plate  IX)  a  somewhat  similar  fall  is  used 
though  the  check  is  vertical.  There  are  a  number  of  these 
falls,  averaging  about  5  feet  in  height  each  and  varying  from 


FIG.  43.— PLAN  AND  CROSS-SECTION  OF  FALL,  BEAR  RIVKK  CANAL. 

1 8  to  21  feet  in  length  on  the  crest.  They  consist  (Fig.  42) 
of  wooden  fluming,  the  flooring  of  which  is  12  feet  in  length 
above  the  fall,  which  rests  on  sheet  piling,  while  the  floor  be- 
low the  fall  is  continued  for  a  length  of  about  16  feet. 

A  somewhat  similar  fall  is  that  employed  on  the  Fresno 
canal,  only  in  this  the  flooring  of  the  apron  below  the  fall  is 


WOOD  EX  FALL    WITH    WATER-CUSHION. 


depressed  i£  feet  below  the  bed  of  the  canal  and  an  earth  fill- 
ing is  placed  above  this,  thus  giving  a  sand  box  on  which  the 
water  falls.  Above  the  crest  of  the  fall  instead  of  the  hori- 
zontal flooring  is  an  inclined  apron  12  feet  in  length  and  slop- 
ing downwards  at  an  angle  of  45  degrees. 

176.  Wooden  Fall  with  Water-cushion. —On  the  Bear 
river  canal  are  a  large  number  of  falls,  ranging  from  4  to  12  feet 
in  height  (Fig.  43).  In  these  the  flooring  has  been  made  es- 
pecially heavy,  and  above  and  below  the  apron  it  slopes  down 
into  the  bed  of  the  canal  to  prevent  percolation.  On  the  line 
of  the  Turlock  canal  in  California  are  falls  varying  from  4  to 
1 1  feet  in  height.  Immediately  above  these  the  canal  is  con- 
tracted from  its  ordinary  bed-width  of  70  feet  to  a  clear  width 
of  40  feet  at  the  fall  crest  in  order  to  reduce  the  velocity  and 
prevent  the  scour  above  it.  These  falls  (Fig.  44)  are  con- 


<---  3 < 


9N.  Pi 

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b  i 

1 


x 


FIG. 


ROSS-SECTION  OF  FALL,  TURI.OCK  CANAL. 


structed  of  wood  much  as  are  those  just  described,  while  below 
the  fall  is  a  depressed  water-cushion  of  such  dimensions  that 
for  a  5-foot  fall  the  water-cushion  is  4  feet  in  depth,  while  the 
i  i-foot  fall  has  a  water-cushion  of  6  feet  in  depth.  Below  the 
water-cushion  a  wooden  apron  is  carried  out  for  16  feet,  while 
a  similar  apron  16  feet  in  length  extends  above  the  fall  crest. 
The  falls  are  divided  into  four  bays  of  10  feet  each  by  means  of 
vertical  rows  of  planking  in  order  to  direct  the  current  and 
prevent  back  eddies. 


MASONRY  FALLS— WOODEN  RAPIDS. 


i67 


177.  Masonry  Falls. — In   all  the  falls  employed  in  India 
masonry  work  alone  is  used.     These  falls  have  sometimes  sim- 
ple vertical  drops,  at  others  they  terminate  in  water-cushions. 
It  is  invariably  csutomary,  however,  in  the  case  of  wide  canals 
to  divide  the  falls  into  bays  of  10  feet  each,  or  thereabouts, 
by  means  of  vertical  partitions  of  masonry  in  order  to  prevent 
scour  and  back  eddy  and  keep  the  water  moving  in  a  direct 
course.     By  this  means  each  may  be  separately  closed  and 
repaired  if  necessary.     An  interesting  series  of  two  falls  ter- 
minating in  water-cushions  on  the  Agra  canal  is  shown  in  cross- 
section  in  Plate  X. 

178.  Wooden   Rapids  or    Chutes. — A   notable  wooden 
rapid  is  the  "  Big  Drop  "  on  the  Grand  River  canal  in  Colo- 
rado.    The  canal  above  the  rapid  is  30  feet  wide  and  4  feet 
deep  and  is  narrowed  down  at  the  head  of  an  inclined  flume 


PLAN     Of    PENSTOCK 

FIG.  45.— PLAN  AND  ELEVATION  OF  BIG  DROP,  GRAND  RIVER  CANAL. 

which  forms  the  rapid  to  a  cross-section  of  5  by  4  feet.  The 
flume  descends  with  a  total  fall  of  35  feet  in  a  length  of  125  feet 
(Fig.  45),  the  water  being  discharged  against  a  solid  bulkhead 
of  timbers  which  throws  it  back  into  a  wooden  penstock. 
From  this  it  escapes  over  a  riffled  floor  16  feet  in  length,  be- 
yond which  is  an  additional  flooring  16  feet  in  length,  whence 
it  emerges  in  the  open  canal. 


1 68 


FALLS  AND   DRAINAGE    WORKS. 


DRAINAGE   WORKS— DRAINAGE   CUTS.  169 

Wooden  rapids  similar  to  those  just  described  are  em- 
ployed on  the  line  of  the  Phyllis  branch  canal  in  Idaho.  These 
are  practically  inclined  wooden  flumes  with  slopes  of  from  I  to 
5  in  100  and  ranging  in  height  from  12  to  50  feet. 

179.  Masonry  Rapids. — On  the  Bari  Doab  canal  in  India 
rapids  paved  with  loose  bowlders  have  been  used  with  great 
success.     The  floors  of  these  rapids  (PI.  XI)  are  confined  be- 
tween low  masonry  walls  so  as  to  prevent  the  movement  of 
the  loose  bowlders,  and  the  banks  are  protected  by  masonry 
wings.     Bowlders  form  a  better  material  for  the  flooring  of  a 
rapid  than   does    brickwork,  which    could   not  safely  be  used 
with  velocities  exceeding   10  feet  per  second.     The  bowlder 
floors  are  grouted    in  mortar  and  will  safely  withstand  a   ve- 
locity of  15  feet  per  second.     The  tail  walls  of  these  rapids  are 
peculiarly  carved  in  order  to  turn  back  the  current  and  pro- 
tect the  canal  banks  from  the  direct  action  of  the  water. 

180.  Drainage   Works. — Where   the   diversion   line  of  a 
canal  is  carried   around  the  sides  of   hills  or  sloping  ground, 
great   difficulties   are  sometimes   encountered  in  passing  side 
drainage.     The  higher  the  canal  heads  up  on  a  stream  the 
more  liable  is  it  to  encounter  cross  drainage.     On  low  slopes 
much    may  be    done    by  diverting    the  watercourses  by  cuts 
emptying  into  natural  drainage   lines.     When  this  cannot  be 
done  it  may  be  passed  in  one  of  the  following  ways : 

1.  By  simple  inlet  dam  ; 

2.  Level  crossing ; 

3.  Flume  or  aqueduct ; 

4.  Superpassage ; 

5.  Culvert  or  inverted  siphon. 

181.  Drainage  Cuts. — An  instructive  example  of  diversion 
by  means  of  a  drainage  cut  is  the  case  of  the  Chuhi  torrent 
on  the  Bari  Doab  canal  in  India.     This  torrent  had  two  out- 
lets, one   running  into  the   Beas  and  the  other  into  the  Ravi 
river  just  above  the  canal  crossing.     The  latter  was  embanked 
close  to  the  bifurcation  by  a  bowlder  dam,  and  by  this  means 
the  water  was  forced  down  the  Beas  and  the  expense  of  cross- 
ing the  canal  saved.     On  the  Betwa  canal  in  India  is  another 


I7O  FALLS  AND   DRAINAGE    WORKS. 

interesting  diversion  cut.  The  first  six  miles  of  this  line  are 
protected  by  a  drainage  channel  15  feet  wide  at  the  bottom 
and  6  feet  deep,  which  runs  parallel  to  the  canal  and  catches 
the  minor  drainage  from  small  streams,  which  it  discharges 
into  the  Betwa  river  above  the  point  of  diversion  of  the  canal. 

182.  Inlet    Dams. — Where    the    drainage    encountered   is 
intermittent  and  its  volume  is  small  relatively  to  that  of  the 
canal,  much  expensive  construction  may  be  saved  by  admitting 
the  water  directly  into  the  canal  and  permitting  it  to  be  dis- 
charged through  the  first  escape   on  its   line.     If   the  canal 
crosses  a  depression  in  the  hillside,  a  heavy  bank  will  of  neces- 
sity be  built  on  its  lower  side  to  keep  the  level  of  its  crest  at 
the  desired  height.     The  result  will  be  to  back  the  water  up 
the  drainage   depression,  thus  causing  wastage  where  water  is 
scarce,  as  the  area  of   surface    exposed    to    evaporation    and 
seepage  is  increased.     In  such  a  case  an  inlet  dam  should  be 
built  at  the  mouth  of  the  depression  to  confine  the  canal  chan- 
nel within  reasonable  limits. 

Inlet  dams  may  be  of  wood,  masonry,  or  loose  stone.  If 
the  depth  of  the  canal  is  small  and  the  consequent  height  of 
overflow  from  the  crest  of  the  dam  to  the  canal  bed  small,  a 
wooden  fluming  or  flooring  may  be  laid  in  the  bed  of  the  canal 
and  a  barrier  or  dam  of  piles  and  sheet  piling  be  built  across 
the  upper  side.  In  the  course  of  a  short  time  the  sediment 
carried  by  the  stream  will  fill  in  behind  the  dam  to  a  level  with 
its  crest  and  the  water  will  simply  fall  over  it  onto  the  wooden 
apron.  The  inlet  dam  may  be  made  as  a  loose  rock  retaining- 
wall  when  the  bed  and  banks  of  the  canal  below  and  opposite 
should  be  riprapped  with  stone  to  protect  them  from  erosion. 
In  case  the  drainage  torrent  is  of  some  magnitude  more  sub- 
stantial works  than  this  may  be  required,  and  it  may  be  neces- 
sary to  build  a  masonry  inlet  dam  and  perhaps  to  build  a  portion 
of  the  canal  channel  of  masonry,  revetting  the  opposite  bank 
with  loose  stone. 

183.  Level  Crossings. — When  the  discharge  of  the  drain- 
age channel  is  large  and  it  is  encountered  at  the  same  level  as 
the  canal,  it  may  be  passed  over,  under,  or  through  the  latter. 


LEVEL    CROSSINGS. 


171 


In  the  latter  case  the  water  is  admitted  by  an  inlet  dam  on  one 
side  and  discharged  through  an  escape  in  the  opposite  bank. 
The  discharge  capacity  of  the  escape  must  be  ample  to  pass 
the  greatest  flood  volume  likely  to  enter,  and  a  set  of  regulat- 
ing gates  must  be  placed  in  the  canal  immediately  below  the 
escape  in  order  that  only  the  proper  amount  of  water  may  be 
permitted  to  pass  down  the  canal.  The  inlet  dam  must  be 
constructed  as  described  in  Article  182,  while  the  escape  and 
regulators  should  be  built  of  the  usual  pattern. 

On  the  line  of  the  Turlock  canal  in  California  are  several 
level  crossings  of  peculiar  design,  built  where  the  canal  skirts 


PPR^j^v^v^ 

>'  £f*o    '  6r     r/te' 


Jn/ef. 


FIG.  46.— PLAN  OF  RUTMOO  CROSSING,  GANGES  CANAT.,  INDIA. 

steep  sidehill  slopes,  causing  the  embankment  on  the  lower 
side  to  become  practically  a  high  earthen  dam.  The  top  of 
the  bank  is  made  a  little  higher,  firmer,  and  wider  than  else- 
where along  the  canal  line,  and  in  the  case  of  two  of  these 
drainage  crossings  no  inlet  dam  has  been  constructed.  As  a 
result  the  water  is  retained  on  the  upper  side  of  the  canal  as  in 
a  large  reservoir.  With  a  new  canal  this  has  no  great  disadvan- 


1/2  FALLS  AND    DRAINAGE    WORKS. 

tage,  as  such  construction  saves  considerable  expense  in  the 
beginning,  while  in  the  course  of  a  few  years,  and  by  the 
time  the  canal  water  becomes  valuable,  this  reservoir  will  have 
silted  up  and  the  canal  can  then  be  confined  between  proper 
limits.  These  earthen  drainage  dams  are  of  considerable 
height,  one  23  feet  and  the  other  40  feet  high,  and  in  them  are 
constructed  escapes,  or  wasteways  for  the  discharge  of  surplus 
waters. 

The  most  interesting  level  crossing  built  is  that  of  the 
Rutmoo  torrent  on  the  Ganges  canal  in  India.  This  consists 
of  a  simple  inlet  at  the  torrent  entrance,  of  a  masonry  outlet 
dam,  of  an  escape  regulator  in  the  opposite  canal  bank,  and  of 
a  regulating  bridge  across  the  canal  channel  just  below  the 
inlet  (Fig.  46).  The  escape  dam  consists  of  47  sluiceways,  each 
10  feet  wide,  with  their  sills  flush  with  the  canal  bed  and 
flanked  on  either  side  with  overfalls  of  the  same  width  with 
their  sills  6  feet  higher,  while  on  the  extreme  flanks  are  plat- 
forms 10  feet  above  the  canal-bed.  The  closing  and  opening 
of  these  sluiceways  is  accomplished  by  means  of  small  flash- 
boards  fitting  into  grooves. 

184.  Flumes  and  Aqueducts. — These  structures  are  prac- 
tically the  same,  the  term  flume  being  more  commonly  em- 
ployed in  this  country  to  mean  a  wooden  structure  for  carrying 
the  waters  of  a  canal  either  around  steep  rocky  hillsides  or  across 
drainage  lines.  The  word  aqueduct  may  be  more  properly 
applied  to  those  flumes  which  are  of  some  magnitude  and  are 
built  of  permanent  material,  as  iron  or  masonry.  Where  the 
drainage  encountered  is  at  a  lower  level  than  the  bed  of  the 
canal,  it  may  most  conveniently  be  passed  under  the  latter, 
which  crosses  over  it  in  a  flume.  Care  must  be  taken  to  study 
the  discharge  of  the  stream  crossed  in  order  that  the  water- 
way under  the  flume  may  be  made  amply  great  to  pass  the 
largest  flood  which  may  occur.  The  foundations  of  the  flume 
must  be  substantial,  and  the  area  of  water-way  must  not  be 
greatly  impeded  ;  otherwise  the  velocity  in  the  drainage  chan- 
nel will  be  so  great  as  to  cause  scour  of  its  bed  and  perhaps 
the  destruction  of  the  work.  Care  must  be  exercised  in  con- 


SIDE  HILL   FLUMES.  1 7  3 

necting  the  ends  of  the  flume  with  the  canal  banks  on  either 
side  so  that  leakage  may  not  occur  at  these  points. 

As  the  flume  or  aqueduct  is  built  across  a  depression,  ex- 
pense in  construction  is  usually  saved  by  limiting  the  length  of 
the  structure  as  much  as  possible.  This  is  done  by  making  its 
approaches  on  either  side  of  earth  embankments,  thus  causing 
the  canal  at  either  end  of  the  flume  to  flow  on  top  of  an  em- 
bankment which  must  be  carefully  constructed  and  of  ample 
width  in  order  that  it  may  not  settle  greatly  or  be  washed 
away.  This  embankment  must  be  faced  with  abutments  and 
wing  walls  at  its  junction  with  the  flume  in  order  to  protect  it 
against  erosion.  That  the  dimensions  of  the  flume  may  be 
as  small  as  possible,  its  cross-section  is  generally  diminished 
and  it  is  given  a  slightly  greater  slope  than  the  canal  at  either 
end  to  enable  it  to  carry  the  required  volume. 

185.  Sidehill  Flumes. — The  simplest  form  of  wooden 
flume  is  what  is  generally  known  as  a  bench  flume,  built  on 
•steep  sidehill  to  save  the  cost  of  canal  excavation.  Such 
flumes  are  common  in  the  West,  notable  examples  of  which 
are  the  bench  flume  on  the  Highline  canal  in  Colorado  (PI.  XII) 
and  the  great  San  Diego  flume  in  California.  The  former  was 
built  to  avoid  expense  in  construction,  its  length  being  a  little 
over  half  a  mile.  It  is  25  feet  wide  and  7  deep,  its  grade  being 
5j  feet  per  mile,  and  its.  discharge  1184  second-feet.  The  San 
Diego  flume,  on  the  other  hand,  was  built  chiefly  to  give  the 
-canal  the  most  permanent  form  of  water-way  and  one  least, 
liable  to  the  losses  of  evaporation  and  absorption.  In  this  case 
fluming  is  employed  for  the  entire  length  of  the  canal,  which  is 
36  miles. 

Such  structures  should  never  be  built  on  embankments; 
they  should  rest  everywhere  on  excavated  material  or  trestles 
to  avoid  the  danger  of  subsidence  and  consequent  destruction. 
This  excavated  bench  should  be  several  feet  wider  than  the 
flume,  in  order  to  give  a  place  on  which  loose  rock  from  the 
sidehills  may  lodge  without  injury  to  the  structure,  and  the 
flume  itself  should  rest  on  a  permanent  foundation  of  mudsills 
or  posts. 


CONSTRUCTION    OF  FLUMES. 


175 


186.  Construction  of  Flumes. — The  boxing  of  flumes  is 
generally  of  three  types  : 

1.  The  floor  may  be    built    directly  on   stringers  and   the 
planking  be  laid  at  right  angles  with  the  current  of  the  stream. 

2.  The  floor  beams  may  be  laid  on  stringers  braced  at  in- 
tervals  calculated  to  bear  the   water  pressure  ;    the    standard 
and  floor  beams  being    boxed   in  and   bolted   to   the   outside 
braces,  the  whole  forming  the  foundation   for  putting  on  the 
inside  sheeting  or  boxing. 

5.  The  floor  beams  and  stringers  may  be  formed  in  cross 
beams  yoked  to  receive  the  boxing. 

The  lumber  forming  the  boxing  of  the  flume  should  be 
from  i  to  2  inches  in  thickness,  according  to  the  dimensions  of 
the  flume,  and  all  joints  should  be  calked  with  oakum.  An 


FIG.  47.— CROPS-SECTION  OF  SAN  DIEGO  FLUME. 

excellent  example  of  bench  flume  is  that  of  the  San  Diego 
Flume  Company  (Fig.  47),  which  is  6  feet  wide  in  the  clear 
and  4  feet  high  ;  the  bottom  and  sides  are  planked  with  2-inch 
redwood,  and  the  boxing  rests  on  transverse  sills  of  2-inch 
planking  laid  4  feet  apart,  and  upon  these  are  4  by  6  longi- 
tudinal stringers,  above  which  is  constructed  the  framework  of 


FLUME    TRESTLES— IRON  AQUEDUCTS.  .177 

the  flume,  consisting  of  4  by  4  scantling  placed  at  intervals  of 
4  feet  and  braced  by  diagonal  uprights  2  by  4  inches  and  3 
feet  in  length. 

187.  Flume  Trestles. — Where  the  flume  crosses  a  depres- 
sion it  rests   on  trestles.     These   are    constructed  as  are   the 
ordinary  trestles  on  railway  lines,  and  are  built  of  various  de- 
signs.    Where    the    trestle   rests    on    dry   ground    it    may   be 
founded  on  mudsills  or  on  short  posts  let   into  the  soil,  but 
where   it  crosses  drainage    channels  it    must  be   substantially 
founded    on   cribs   or  piling.     The   superstructure  of  a  flume 
crossing  a  drainage  line  is   similar  to  that  of  bench  flumes.     A 
large  and  imposing  flume  is  that  across  the  Pecos  river  in  New 
Mexico  (PI.  XIII).     The  approaches  to  this  flume  consist  of  a 
terre  plein  or  raised  embankment  105  feet  wide  at  the  base,  24 
feet  in  maximum  height,  and  80  feet  wide  on  the  top,  while 
the  top   width  of  the  canal  is   70  feet,  thus  giving  5  feet  in 
width  of  embankment  for  the  canal  channel.     The  flume  ter- 
minates at  either  end  in  substantial  wooden  wings  extending 
for  12  feet  into  the  earth  embankments  and  well  braced  and 
supported  by  sheet  and  anchor  piling.     This  flume  is  40  feet  in 
height  above  the  river,  25  feet  wide,  8  feet  deep,  and  475  feet 
long,  and  rests  on  a  substantial  trestlework,  the  spans  of  which 
are  16  feet  in  length. 

188.  Iron  Aqueducts. — But  few  of  these  have  been  con- 
structed, though  it  is  probable  that  they  will  continue  to  grow 
in  favor  and  will  be  largely  substituted  for  wood.     The  chief 
difficulty  encountered  in  constructing  long  aqueducts  of  iron 
has  been  the  expansion  and  contraction  of  the  metal,  though 
in  fact  this  has  proven  to  be  an  imaginary  rather  than  a  real 
danger.     In  practice  it  has   been   found  that  the  metal  of  the 
structure  has  approximately  the  same  temperature  as  that  of 
the  water,  and  as  this  is  somewhat  uniform  but  little  change 
takes  place  in  the  dimensions  of  the  aqueduct.     On  the  Bear 
River  canal  in  Utah  are  two  aqueducts,  one  of  which  consists 
of  a  wooden  flume  resting  on  iron  trestles  founded  on  masonry 
columns.     The  other  is  a  simple  iron  aqueduct  resting  on  iron 
trestles.     The  floor  of  this  is  37  feet  above  the  bed  of  the 


1/8 


FALLS  AND  DRAINAGE    WORKS. 


stream,  and  its  length  is  1 30  feet  (Fig.  48),  disposed  in  three  bents 
the  centre  span  of  which  is  60  feet  long,  the  other  two  being 
respectively  25  and  45  feet  long.  This  aqueduct  is  essentially  a 
plate-girder  bridge  resting  on  iron  columns  and  founded  on  iron 


I  "_'«?< ".x. "_, 


.130' 


HI  I   I  I   [  ,  J 


i  M  1 1  n  LI 


FIG.  48.— BEAR  RIVER  CANAL.    ELEVATION  AND  CROSS-SECTION  OF  IRON  FLUME  ON  CORINNE 

BRANCH. 

cylinders  filled  with  concrete  and  resting  on  piles.  The  plate 
girders  forming  the  sides  of  the  aqueduct  are  5^  feet  in  depth, 
the  available  depth  of  water  being  4  feet.  The  sides  of  the 
girder  are  braced  by  vertical  angle-iron  riveted  to  it  every  5 
feet  apart,  while  the  top  is  cross-braced  by  similar  angle-iron. 


IRON  AQUEDUCTS. 


179 


These  angle-irons  vary  between  3  and  4  inches  in  width,  while 
the  web  of  the  sides  of  the  aqueduct  consists  of  -f-inch  iron. 

On  the  Henares  canal  in  Spain  is  an  iron  aqueduct  over 
the  Majanar  torrent.  This  aqueduct  is  70  feet  long  with  a 
clear  span  of  62  feet.  Its  water-way  is  10.17  ^eet  wide,  its 
capacity  being  177  second-feet.  The  sides  are  composed  of 
box  girders  6.2  feet  deep  (Fig.  49),  and  each  girder  is  calculated 


Half  5/evarion  of  Aqueduct 


1-t-HtHjfl 


FIG.  49. — AQUF.DUCT,  HENARES  CANAL,  SPAIN. 

to  bear  200  tons  or  the  entire  structure  to  carry  400  tons.  To 
prevent  leakage  the  ends  of  the  aqueduct  rest  on  stone  tem- 
plates, and  4  inches  from  each  end  is  a  pillow  composed  of 
long  strips  of  felt  carpet  9  inches  wide  and  soaked  in  tallow, 
which  is  let  into  the  stone  below  the  aqueduct.  This  presses 
on  it  with  its  full  weight,  thus  making  a  water-tight  joint.  In 
addition  to  this  lead  flushing  is  riveted  to  the  aqueduct  and 
let  into  a  recess  of  the  stone  abutments.  This  recess  is  12 
inches  deep  and  4  inches  wide,  and  around  it  is  poured,  hot,  a 


MASONRY  AQUEDUCTS— SUPERP  A  SSAGES.  l8l 

mixture  of  tar,  pitch,  and  sand,  which  allows  slight  play  during 
its  expansion  and  contraction  and  yet  is  water-tight, 

189.  Masonry    Aqueducts. — In    general    design    masonry 
aqueducts  are  planned  and  constructed  much  as  are  those  of 
wood  or  iron.     One  of  the  greatest  structures  of  this  kind  is 
the  Solani  aqueduct  on  the  Ganges  canal  in   India  (PL  XIV). 
This  consists  of  an  earth  embankment  approach  or  terre  plein 
2f  miles  in  length  across  the  Solani  valley,  its  greatest  height 
being  24  feet.     This  embankment  is  350  feet  wide  at  the  base 
and  290  feet  wide    on  top,  and  on    this  the  canal  banks    are 
formed,  the  width  of  the  banks  being  30  feet  on  top  and  the 
bed-width  of  the  canal   150  feet.     The  aqueduct  is  920  feet  in 
length  with  a  clear  water  space  between  piers  of  750  feet,  dis- 
posed in  fifteen  spans  of  50  feet  each.     The  breadth  of  each 
arch  parallel  to  the  channel  of  the  river  is  192  feet  audits  thick- 
ness 5  feet.     The   greatest  height  of  the  aqueduct  above  the 
river  valley  is  38  feet,  and   the  walls  of  the  water-way  are  8 
feet  thick  and  12   feet   deep.     This   structure   is   founded   on 
masonry  piers  resting  on  wells  sunk  20  feet  in  the  river  bed. 

Perhaps  the  most  magnificent  aqueduct  ever  built  is  that 
carrying  the  Lower  Ganges  canal  across  the  Kali  Nadi  torrent 
in  India  (Plate  XV).  The  present  structure  was  built  to  replace 
another  of  similar  design  which  was  destroyed  by  a  flood 
which  the  water-way  under  the  aqueduct  was  too  small  to 
pass.  This  was  calculated  to  discharge  30,000  second-feet, 
\vhereas  the  flood  which  destroyed  it  amounted  to  135,000 
second-feet  in  volume.  The  present  aqueduct  consists  of  fif- 
teen masonry  spans  each  50  feet  in  width  and  supported  on 
masonry  wells  sunk  to  a  maximum  depth  of  50  feet.  Under 
the  aqueduct  is  built  up  a  concrete  floor  5  feet  in  thickness  to 
prevent  erosion  and  destruction  of  the  foundation. 

190.  Superpassages. — Where  the  canal  is  at  a  lower  level 
than  the  drainage  channel,  a  superpassage  is  employed  to  carry 
the    latter  over  the  canal.     A    superpassage  is  practically  an 
aqueduct,  though  there  are   some  elements  entering  into    its 
design   which    are    different    from    those    affecting  aqueducts. 
The  volumes  of  streams  which  are  to  be  carried  in  superpas- 


182 


FALLS  AND   DRAINAGE    WORKS. 


HEM.  O 


PLATE  XV. — ELEVATION  AND  CROSS-SECTION  OF  NADRAI  AQUEDUCT,  LOWER  GANGES 

CANAL,  INDIA. 


SUPERPA  SSA  GES.  1 8  3 

sages  are  variable ;  at  times  they  may  be  dry,  while  at  others 
their  flood  discharges  may  be  enormous.  No  provision  has  to 
to  be  made  for  passing  flood  waters  under  the  structure,  since 
the  discharge  of  the  canal  beneath  it  is  fixed.  On  the  other 
hand,  the  water-way  of  the  superpassage  must  be  made  amply 
large  to  carry  the  greatest  flood  which  may  occur  in  the  stream, 
and  much  care  must  be  taken  in  joining  the  superpassage  to 
the  stream  bed  above  and  below  to  prevent?  injury  by  the 
violent  action  of  the  flood  waters. 

No  instances  can  be  cited  where  superpassages  have  been 
constructed  in  the  United  States.  In  nearly  every  case  where 
these  would  have  been  required  the  canal  has  been  taken  under 
the  stream-bed  in  an  inverted  siphon.  In  India,  however, 
superpassages  have  frequently  been  used  on  the  canals,  where 
they  have  been  employed  in  preference  to  inverted  siphons 
chiefly  because  of  the  requirements  of  navigation.  It  would 
probably  be  a  dangerous  experiment  to  attempt  to  construct  a 
superpassage  of  wood,  because  it  would  be  so  constantly  sub- 
jected to  alternate  drying  and  wetting,  according  as  there  was 
or  was  not  water  flowing  in  the  stream,  that  it  would  soon 
decay.  A  small  iron  superpassage  has  been  constructed  across 
the  Agra  canal  in  India  which  is  99  feet  long,  30  wide,  10 
feet  deep,  and  is  constructed  of  boiler-iron  strongly  cross- 
braced.  It  is  well  built  and  is  supported  on  masonry  piers. 
Its  slope  is  steep,  thus  giving  a  high  velocity.  The  connection 
between  its  ends  and  the  abutments  is  made  by  means  of 
heavy  sheet  lead  to  accommodate  the  changes  due  to  expan- 
sion of  the  iron.  This  precaution  is  more  necessary  in  a  super- 
passage  than  in  an  aqueduct,  as  it  is  more  subject  to  changes 
of  temperature  when  empty. 

On  the  Ganges  canal  in  India  are  two  of  the  largest  and 
most  interesting  superpassages  ever  constructed.  One  carries 
the  Puthri  torrent  and  the  other  the  Ranipur  torrent  over  the 
canal.  The  discharge  of  the  former  amounts  in  times  of  flood 
to  as  much  as  15,000  second-feet.  The  Ranipur  superpassage 
(PI.  XVI)  is  built  of  masonry  founded  on  wells,  and  its  flooring, 
which  is  given  a  steep  slope  in  order  that  the  velocity  shall 


INVERTED   SIPHONS.  185 

prevent  its  filling  up  with  sediment,  is  3  feet  in  thickness  above 
the  crown  of  the  arches  and  is  bordered  by  parapets  7  feet 
wide  and  4  feet  high.  The  flooring  and  parapets  continue 
inland  from  the  body  of  the  work  a  distance  of  100  feet  on 
each  side,  the  latter  expanding  outward  so  as  to  form  wings  to 
keep  the  water  within  bounds,  The  superpassage  is  300  feet 
long  and  provides  a  water-way  195  feet  wide  and  6  feet  deep. 

191.  Inverted  Siphons. — Where  the  canal  is  not  used  for 
purposes  of  navigation  and  encounters  drainage  at  a  relatively 
low  level,  the  most  convenient  and  usual  form  of  crossing  is  by 
means  of  inverted  siphons.    The  ordinary  method  of  using  these 
is  to   carry  the  water  of  the  canal  in  the   siphons  under  the 
stream,  though  sometimes  the  stream  is  carried  in  the  siphon 
and  the  canal  is  taken  over  this  in  a  half  aqueduct.     The  di- 
mensions of  the  siphon  are  to  be  computed  by  means  of  one 
of  tlje   many   formulas  for  the   flow  of  water  through   pipes, 
though  the  formula  for  flow  through   channels  may  also  be 
used  in  some  cases.     Many  examples  of  these  are  to  be  found 
in  works  on  hydraulics,  and  therefore  they  will  be  but  briefly 
referred  to  here. 

To  find  the  velocity  of  flow  in  a  pipe,  given  its  diameter, 
length,  fall,  and  value  of  n,  or  the  coefficient  of  roughness,  we 
can  use  the  formula  v  =  c  Vrs.  To  determine  the  discharge  we 
can  use  the  formula  Q  =  av,  or  the  velocity  into  the  cross- 
section.  The  various  other  dimensions  of  the  pipe,  such  as  the 
velocity  and  grade  given  to  find  its  diameter,  are  obtained  in 
like  manner  from  these  formulas  by  looking  up  their  equivalent 
values  in  published  tables. 

192.  Inverted  Siphon  of  Wood. — An  excellent  example  of 
a  small  work    of  this  kind  is   the  wooden  culvert  or  inverted 
siphon  used  on  the   Del   Norte   canal   in    Colorado  (Fig.  50). 
This  consists  of  two  parallel  wooden  boxes,  each  4  feet  6  inches 
wide  by  3  feet  high,  supported  on  piling  and  framed  and  braced 
with  6  by  8  scantling.     The  bottom  and  sides  are  floored  with 
2-inch  plank,  while  the  top,  which  has  to  bear  the  weight  of  the 
superincumbent  earth  and  water,  is  covered  with  6-inch  plank- 
ing laid  crosswise. 


1 86 


FALLS  AND  DRAINAGE    WORKS. 


A  most  interesting  wooden- 
siphon  is  that  which  carries  the 
Central  Irrigation  District  canal 
under  Stony  creek  in  Colusa  county, 
California.  In  addition  to  acting 
as  a  conduit  for  the  waters  of  the 
canal  it  is  so  arranged  as  to  act  as 
an  escape  and  regulating  gate  to  the 
canal,  while  its  crest  acts  as  an  in- 
let from  the  creek.  The  length  of 
the  siphon  is  650  feet,  and  it  ter- 
minates at  either  end  in  an  inlet 
and  outlet  masonry  well  protected 
by;substantial  walls  and  approaches, 
as  shown  in  PL  XVII.  This  siphon 
consists  of  seven  parallel  lines  of 
semicircular  wooden  tubing  fastened 
under  a  horizontal  platform  of  wood 
the  top  of  which  is  level  with  the 
stream-bed.  Above  and  below  the 
platform  in  the  creek-bed  are 
wooden  aprons,  while  light  training 
works  keep  the  current  of  the  stream 
in  its  channel.  At  the  inlet  to  the 
culvert  are  a  set  of  simple  flash- 
board  regulating  gates  which  act  as 
an  escape  to  the  canal.  The  outlet 
culvert-well  is  planned  as  a  simple 
inlet  to  the  canal.  As  shown  in  the 
illustration,  the  semicircular  wooden 
culvert  rests  on  a  bed  of  concrete 
l\  feet  in  thickness.  The  tubes  of 
the  culvert  are  each  5  feet  5  inches 
in  diameter  and  consist  of  2^-inch 
staves  laid  longitudinally  and  bound 
together  by  semicircular  iron  hoops 
which  terminate  in  bolts  above  the 
platform  floor. 


INVERTED    SIPHON   OF    WOOD. 


I87 


r 


PLATE    XVII.— CENTRAL  IRRIGATION  DISTRICT  CANAL.      ELEVATION  AND  CROSS-SECTION  ot 
STONY  CREEK  CULVERT. 


PLATE  XVIII.— IDAHO  IRRIGATION  COMPANY'S  CANAL.    VIEW  OF  WOODEN  SIPHON  ON  PHYLDS 

BRANCH. 

1 88 


INVERTED   SIPHONS  OF  MASONRY. 


I89 


Instead  of  this  form  of  built-up  wooden  inverted  siphon, 
ordinary  wrought-iron,  cement,  or  wooden  pipes  are  frequently 
employed,  especially  where  the  head  is  great.  These  wooden 


Gaoutio  Sutrrxee 


FIG.  51.  —  SOANE  CANAL.    CROSS-SECTION  OF  KAO  NULLA  SIPHON-AQUEDUCT. 

pipes  may  be  of  the  ordinary  wrought-iron  hydraulic  mining 
type  or  of  the  same  type  as  the  Colorado  wooden  pipe  de- 
scribed in  article  204  (PL  XVIII). 

193.  Inverted  Siphons  of  Masonry.  —  An  interesting  struc- 
ture of  this  kind  which  is  practically  a  siphon  aqueduct,  since 
the  waters  of  the  stream  are  carried  under  those  of  the  canal, 
is  that  carrying  the  Kao  torrent  under  the  Soane  canal  in 
India  (Fig.  51).  This  work  is  built  of  the  most  substantial 
masonry,  the  area  of  the  superstructure  being  contracted  and 
given  a  slightly  increased  grade  to  carry  the  waters  of  the 
canal,  while  the  waters  of  the  torrent  flow  over  a  masonry 
floor  which  is  depressed  a  few  feet. 

The  most  magnificent  masonry  siphon  ever  built  is  that 
carrying  the  waters  of  the  Cavour  canal  under  the  Sesia  river 
in  Italy.  Its  total  length  is  878  feet  and  it  consists  of  five  oval 
orifices  (Fig.  52)  each  7.8  feet  in  height  by  16.2  feet  in  width, 
the  amount  of  depression  of  the  water  surface  in  the  canal  be- 


UNIVERSITY  ) 

d/.r  ,,,A          // 


190 


FALLS  AND  DRAINAGE    WORKS. 


ing  7^  feet.  The  siphon  consists  of  a  substantial  concrete  floor 
or  foundation  iijfeet  in  thickness  under  the  river  bed,  its 
roof  forming  the  floor  of  the  river  channel  and  being  about  3 


FIG.  52.— SECTIONS  OF  SESIA  SIPHON,  CAVOUR  CANAL,  ITALY. 

feet  in  thickness.  Another  large  siphon  is  that  on  the  Sirhind 
canal  in  India  crossing  the  Hurron  torrent.  The  total  length 
of  this  is  212  feet,  and  it  consists  of  two  openings  each  4 
feet  high  by  15  feet  wide.  The  water  drops  from  the  canal 
almost  vertically  into  a  well  the  floor  of  which  is  on  a  level 
with  the  floor  of  the  siphon,  while  at  its  exit  it  is  raised  again 
to  the  level  of  the  outlet  canal  up  an  incline  built  in  steps. 


CHAPTER  XV. 
DISTRIBUTARIES. 

194.  Object  and  Types. — Distributaries  are  to  a  main  ca- 
nal system  what  service  pipes  are  to  the  mains  in  city  water 
service.     The  minor  ditches  or  laterals  which  are  owned  by 
the  irrigators  and  from  which  water  is  directly  applied  to  the 
crops  should  never  be  diverted  from  the  main  canal  nor  from 
its  upper  branches.     It  is  desirable  to  have  as  few  openings  in 
the  bank  of  the  main  canal  as  possible,  so  as  to  reduce  to  a 
minimum    the    liability  of  accident.     The  water  is  drawn   at 
proper    intervals    from    the    main    line    into    moderate-sized 
branches  which  are  so  arranged  as  to  command  the    greatest 
area  of  land  and  to  supply  the  laterals  and   small   ditches  of 
the  irrigators   in   the   most  direct   manner.     Wherever  water 
has  not  a  high  intrinsic  value  it  is  conducted  to  the  lands  in 
open  distributaries  and  laterals  excavated  in  the  earth.     Where, 
however,  its  value  is  relatively  high  and  it  is  scarce  it  is  desir- 
able to  reduce  the  losses  from  percolation  and  evaporation  to 
a  minimum.     In  such  cases  the  distributaries  consist  of  wooden 
flumes  or  of  paved  or  masonry-lined  earth   channels,  while  in 
extreme  cases,  such  as  are  frequently  encountered  in  Southern 
California,  water  is  conducted   underground   to  the  point  of 
application  in   pipes,  and  is  applied  to  the  crops  from  these 
instead  of  being  flowed  over  the  surface.     By  such  methods  of 
handling  the  highest  possible  duty  is  obtained  and   the  most 
effective  use  made  of  the  water  at  command. 

195.  Location   of    Distributaries. — Distribution    from   a 
canal   is    most:  economically  effected  when   it   runs  along  the 
summit  of  a  ridge  so  that  it  can  supply  water  to  its  branches 

191 


I Q2  DIS  TRIE  U  TA  RIES. 

and  to  private  channels  on  either  side.  In  the  case  of  main 
canals  this  location  can  be  made  only  in  occasional  instances  ; 
but  the  distributaries  taken  from  these  mains  should  be  made 
to  conform  to  the  dividing  lines  between  watercourses.  The 
capacity  of  the  distributaries  which  then  traverse  the  separate 
drainage  divides  are  proportioned  to  the  duties  they  have  to 
perform,  the  natural  bounding  streams  limiting  the  area  they 
have  to  irrigate. 

In  designing  a  distributary  system  too  little  care  and  atten- 
tion are  ordinarily  paid  to  its  proper  location  and  survey ;  yet 
it  is  in  the  distribution  and  handling  of  water  that  the  greatest 
losses  occur,  and  accordingly  it  is  there  that  the  greatest  care 
should  be  taken  in  its  transportation.  Careful  surveys  should 
be  made  of  the  area  to  be  traversed  by  the  distributaries,  as 
described  in  Chapter  XI  for  the  location  of  main  canals,  and 
the  greatest  care  should  be  taken  to  balance  cuts  and  fills  and 
to  so  locate  the  distributaries  that  the  least  loss  of  water  shall 
occur  from  percolation. 

In  Fig.  53  is  shown  an  ideal  distributary  system.     The  con- 


FIG.  53. — DIAGRAM   ILLUSTKATING  DISTRIBUTARY  SYSTEM. 

tour  lines  and  drainage  courses  show  the  general  slope  and  lay 
of  the  country,  and  the  main  canal  and  its  tributaries  should 
be  run  down  the  divides  between  these  drainage  lines  as  indi- 


DESIGN  OF  DISTRIBUTARIES.  193 

cated.  Such  an  arrangement  enables  the  least  mileage  of 
channels  to  command  the  greatest  area  of  country  by  furnish- 
ing water  to  both  sides  of  its  line.  At  the  same  time  perfect 
drainage  is  obtained  by  the  water  flowing  in  both  directions 
into  the  natural  watercourses. 

t"  196.  Design  of  Distributaries. — For  the  more  complete 
and  efficient  distribution  of  water  the  engineer  treats  distribu- 
taries as  of  as  much  importance  as  the  main  branches.  At- 
tention is  devoted  to  the  character  of  the  soil  traversed,  to 
the  alignment,  to  the  safe  and  permanent  crossing  of  natural 
drainage  lines,  and  especially  to  so  maintaining  the  surface  of 
the  canal  with  relation  to  the  ground  as  to  command  the 
largest  irrigable  area.  In  all  well-designed  distributary  sys- 
tems the  capacity  of  the  channels  is  exactly  proportioned  to 
the  duty  to  be  performed,  the  cross-sectional  area  being  dimin- 
ished as  the  quantity  of  water  is  decreased  by  its  diversion  to 
private  watercourses. 

The  distributary  should  be  taken  off  from  the  main  canal  as 
near  the  surface  of  the  latter  as  possible.  That  is,  the  bed  of 
the  distributary  should  not  be  on  a  level  with  the  bed  of  the 
canal,  but  should  be  placed  with  reference  to  the  full  supply 
of  the  main  canal,  in  order  to  get  the  clearest  water,  and  in 
order  that  the  bed  of  the  distributary  may  be  kept  at  a  high 
level  and  admit  of  surface  irrigation  throughout  its  length. 
In  leyel  country  great  care  should  be  taken  in  designing 
distributaries  that  the  natural  drainage  lines  into  which 
they  tail  shall  be  sufficiently  large  to  accommodate  any  flood 
volume  it  may  be  necessary  to  pour  into  them  ;  otherwise  the 
stream  courses  might  become  clogged  and  flood  the  surround- 
ing country.  In  order  to  avoid  the  construction  of  costly  em- 
bankments and  to  insure  the  surface  of  the  water  being  above 
that  of  the  country,  the  slope  of  the  distributary  should  be 
made  as  nearly  parallel  as  possible  to  that  of  the  land  it  trav- 
erses. To  effect  this  alignment  falls  must  be  frequently  in- 
troduced ;  and  to  dispose  of  storm-waters  escapes  into  natural 
drainage  lines  should  be  provided  at  least  every  10  miles  in 
the  course  of  the  distributary.  .s 


1 94  DIS  TRIE  UTA  R1ES. 

196.  Efficiency  of  a  Canal. — According  to  Mr.  J.  S.  Beres- 
ford,  an  Indian  engineer,  we  may  look  upon  a  great  canal  sys- 
tem as  a  machine  composed  of  four  parts  and  calculate  its 
efficiency  in  the  same  way  as  that  of  a  steam-engine.  These 
parts  are : 

1.  The  main  canal  ; 

2.  The  distributaries; 

3.  The  private  irrigating  channels ; 

4.  The  cultivators  who  apply  the  water  to  the  soil. 

Each  cubic  foot  of  water  entering  the  canal  head  is  ex- 
pended in  five  ways : 

1.  In  waste  by  absorption  and  evaporation  in  passing  from 
the  canal  head  to  the  distributary  head. 

2.  In  waste  from  the  same  causes  between  the  distributary 
head  and  the  head  of  the  private  channel. 

3.  In  waste  from  the  same  causes  in  passing  from  the  pri- 
vate channel  to  the  field  to  be  watered. 

4.  In  waste  by  the  cultivators  in  handling  the  water,  both 
by  causing  losses  from  evaporation  or  from  percolation  where 
an  unnecessary  amount  is  applied. 

5.  In  useful  irrigation  of  the  land. 

The  object  is  plainly  to  increase  the  last  item  by  the  reduc- 
tion of  all  the  rest.  Calling  Dl  the  theoretic  duty  of  a  foot  of 
water  entering  the  canal  head,  we  have  the  actual  duty  of  the 

canal 

D  =  Cme  X  D\ (i) 

where  Cme  represents  the  mean  efficiency  of  the  main  canal. 
Now  if  the  efficiency  of  water  entering  a  distributary  head  for 
use  in  watering  a  field  from  an  outlet  is  called  E,  the  duty  of 
water  used  in  this  field  will  be 

D  =  EX& (2) 

and 

E  =  EdXEwXEc, (3) 

where  Ed  is  the  efficiency  of  the  distributary,  Ew  is  the  effi- 
ciency of  the  private  watercourse  between  its  head  and  the 


EFFICIENCY   OF  A    CANAL.  1  95 

field,  and  Ec  is  the  efficiency  of  the  cultivator  who  waters  the 
field. 

The  efficiency  of  any  distributary  is  the  fraction  whose  de- 
nominator is  the  quantity  entering  the  distributary  head,  and 
the  numerator  this  same  quantity  minus  the  loss  down  to  the 
point  in  question.  If  W  represents  the  waste  down  to  any 
outlet,  Q  the  discharge  at  the  head  of  the  distributary,  and 
E°  the  efficiency  at  the  point  under  consideration,  then 

.     Q  -  w          w 


The  waste  W,  down  to  any  point  may  approximately  be  ex- 
pressed as  the  product  of  the  loss  of  the  first  mile  into  some 
function  of  the  length,  or 


L*;     .......     (5) 

or  substituting  in  the  above  equation,  we  get 

APxL*  ,,, 

E  —Q  -  >     ......        (6) 

where  AP  is  the  ascertained  loss  by  absorption  and  percolation 
in  the  first  mile  and  L*  is  some  function  of  the  length,  which 
will  be  found  by  experiment  to  be  about  \  or  f  of  L  in  most 
cases,  or  near  the  head  of  the  distributary  Z-1. 

Taking  /  as  the  length  of  the  private  watercourse,  q  as  its 
discharge,  and  /*  as  the  same  function  of  its  length  as  in  the 
case  of  Lx,  we  have  the  efficiency  of  the  private  channel 


w 


The  efficiency  of  the  cultivator  Ee  varies  between  .5  and  .9 
where  unity  represents  his  efficiency  at  the  theoretical  limit. 
Now  for  an  outlet  at  the  head  of  the  distributary  and  with 
the  irrigating  field  close  to  this  outlet.  Z  —  o  and  /=o. 


1  96  DIS  TRIE  U  TA  RIE  S. 

Therefore  the  second  terms  of  the  equations  (6)  and  (7)  van- 
ish and  E°  and  E™  =  o. 

An  application  of  these  rules  as  laid  down  by  Mr.  Beres- 
ford  is  given  in  the  following  cases  :  Say  the  discharge 
Q  =  50  cubic  feet  ;  that  the  outlet  is  at  the  loth  mile,  whence 
L=  10;  the  losses  from  percolation,  etc.,  being  1.25  in  the 
first  mile  and  x  =  $.  The  discharge  of  the  watercourse 
q  =  i  cubic  foot,  /  =  6  furlongs,  and  ap  =  .03  of  a  cubic  foot 
per  furlong.  Then 


say     £'=75; 

and     E  =  .829  X  .82  X  -75  =  -5  1  5 

or  leaving  out  the  cultivator,  this  is  equal  to  .68.  That  is,  of 
each  cubic  foot  entering  the  distributary  head  only  .68  of  a 
cubic  foot  is  available  at  the  loth  mile  and  6  furlongs.  What- 
ever the  actual  amount  of  loss  in  either  distributary  or  private 
channel,  it  varies  directly  with  L  and  /;  it  also  varies  directly 
with  AP  and  ap,  and  great  waste  is  due  to  the  cultivator  if  he 
is  careless.  It  will  thus  be  seen  from  the  above  that  every 
effort  should  be  made  to  reduce  the  value  of  AP  and  to  induce 
the  cultivator  to  use  the  greatest  possible  care  in  handling  the 
water. 

198.  Private  Watercourses.  —  As  a  result  of  Mr.  Beres- 
ford's  experiments  it  is  evident  that  the  widest  field  for 
improvement  is  in  the  private  watercourses.  As  generally 
constructed  these  are  much  longer  than  is  necessary,  and  are 
usually  so  constructed  as  to  avoid  low  lands,  whereas  flumes 
or  proper  alignment  would  remedy  this.  They  often  run  long 
distances  through  sandy  soil,  which  absorbs  the  water,  and 
frequently  parallel  each  other,  thus  adding  to  the  losses  by 
absorption  by  unnecessarily  increasing  the  wetted  perimeter. 


DIMENSIONS  OF  DISTRIBUTARIES.  1 97 

Where  sandy  soil  is  encountered  or  depressions  are  to  be 
crossed  the  channels  should  be  puddled  or  flumes  employed. 

199.  Dimensions  of  Distributaries. — Experiments  made  in 
India  show  that  the  greater  the  amount  of  water  discharged 
by  a  distributary  the  smaller  will  be  the  proportion  of  cost  of 
maintenance.  Thus  a  channel  12  feet  wide  discharges  more 
than  double  the  volume  discharged  by  two  channels  each  6 
feet  wide,  while  the  cost  of  patrolling  and  repairing  the  banks 
would  be  half  that  of  both  the  smaller  ones.  Experience  has 
proved  that  irrigation  can  be  most  profitably  carried  on  from 
channels  18  feet  wide  at  the  bottom  and  carrying  about  4  feet 
in  depth  of  water.  Thus  on  the  eastern  Jumna  canals  during 
the  years  1858  to  1860,  inclusive,  the  expenditure  of  water  on 
all  the  distributaries  of  12  feet  bed-width  and  upwards  was 
0.123  of  the  revenue,  while  on  all  those  below  12  feet  it  was 
0.223  or  nearly  double  that  of  the  first.  From  the  same  ex- 
aminations the  relative  value  per  cubic  foot  per  annum  on 
channels  of  respectively  12,  6,  and  3  feet  in  bed-width  was  as 
10  :  7  :  4-  The  increased  action  of  absorption  in  small  chan- 
nels with  diminished  volumes  and  velocities  accounts  for  the 
difference.  The  depth  of  water  should  accordingly  seldom  be 
less  than  4  feet  and  the  surface  of  the  water  should  be  kept  at 
from  I  to  3  feet  above  that  of  the  surrounding  country  ;  not 
only  to  afford  gravity  irrigation,  but  because  the  loss  by  absorp- 
tion is  thereby  diminished. 

The  principle  which  is  so  commonly  employed  in  the  West 
on  minor  private  channels  of  diverting  the  water  by  raising  it 
to  the  surface  of  the  country  by  means  of  earth  check-dams, 
or  by  introducing  plank  stops  in  grooves,  is  to  be  condemned. 
It  converts  freely  flowing  streams  into  stagnant  pools,  encour- 
ages the  growth  of  weeds  and  the  deposit  of  silt,  and  produces 
an  unhealthy  condition  of  the  neighborhood.  It  is  moreover 
extremely  wasteful  of  water,  since  much  of  the  latter  is  dis- 
sipated because  of  loss  of  head  and  because  of  absorption  and 
evaporation.  Where  these  stop  planks  or  checks  are  used  in 
private  channels  with  a  view  to  diverting  the  water  to  the  irri- 
gable fields,  little  or  no  damage  is  done,  since  the  planks  re- 


1 98  DIS  TRIE  U  TA  KIE  S. 

main  in  but  a  short  time,  during  which  no  damage  is  likely  to 
occur. 

200.  Distributary  Channels  in  Earth. — The  cross-section 
of  the  main   or  larger   distributaries   should  be  relatively  the 
same  as  for  main  canals  (Articles  117  to  120.)     In  designing 
the  canal  banks  their  top  width  should  be  sufficient  to  admit 
of  easy  inspection.      On  moderate-sized  distributaries  3  feet 
may  be  taken  as  the  minimum  width.     Should  the  cut  not  be  so 
deep  that  a  berm  is  necessary,  it  is  always  well  to  let  the  latter 
slope  away  from  the  canal  and  be  drained  off  through  the  bank. 
The  top  of  the  bank  likewise  should  not  be  level   but  should 
drain    away    from    the    canal.     For    smaller   distributaries    or 
minor  private  channels  a  small  trapezoidal  cross-section  both 
for  the  bank  and  the  canal  will  usually  be  sufficient,  and  as  far 
as  possible  the  larger  portion  of  this  cross-section  should  be  in 
embankment,  thus   keeping  the  water  above  the  level  of  the 
surrounding   country.     In  such  small  channels  it  is  not  neces- 
sary to  construct  berms,  to  give  subgrades  or  other  complex 
cross-sections. 

201.  Wooden  Distributary  Heads. — Distributary  heads  on 
Western  canals  are  arranged  much  as  are   the  heads  of  main 
canals  and  escapes.     They  consist  essentially  of  two  parts,  a 
regulator  or  check  below  the  head  on  the  main  canal,  in  order 
to  divert  the  water  into  the  distributary,  and  a  regulating  gate 
in  the  latter  to   admit  the  proper  amount  of  water.     These 
heads  usually  consist  of  a  wooden  fluming,  which  is  practically 
an  apron  to  the  bed  of  the  distributary  and  planking  to  protect 
the  banks.     Inthis  fluming  are   inserted  the  gates,  which  con- 
sist either  of  flash  boards,  as  in  Kern  county,  California,  or  of 
simple  wooden  lifting  gates,  as  in  most  other  portions  of  the 
West. 

In  Fig.  54  is  shown  a  distributary  head  on  the  line  of  the 
Calloway  canal  in  California.  Immediately  below  the  regu- 
lator is  shown  a  minor  headgate  leading  to  a  private  channel, 
while  a  sort  of  well  is  formed  in  the  distributary  flume  just  be- 
low this  minor  headgate  to  retard  the  velocity  of  the  current. 
On  the  line  of  the  Idaho  canal  the  distributary  heads  are 


WOODEN  DISTRIBUTARY  HEADS. 


I99 


FIG.  54.— VIEW  OF  DISTRIBUTARY  HEAD,  CALLOWAY  CANAL. 

designed  much   as   are   the   main  heads   on   the   same  canal 
(Fig.  40). 

On  the  Del  Norte  canal  in  Colorado  a  few  of  the  distribu- 


FIG.  55. — PLAN  OF  BIFURCATION,  DEL  NORTE  CANAL. 

taries  are  diverted  by  practically  bifurcating  the  main  branch, 
the  latter  thus  terminating  in  two  distributaries,  in  the  heads 
of  which  are  placed  regulating  gates  (Fig.  55). 


2OO 


DISTRIBUTARIES. 


DISTRIBUTARY  HEADS— DISTRIBUTARY  PIPES.       2OI 

202.  Masonry  Distributary  Heads. — In  Europe  and  India 
masonry  is  employed  almost  exclusively  in  the  construction  of 
distributary  heads.  These  are  generally  so  built  that  the 
water  passing  from  them  can  be  measured  and  the  volume 
turned  into  the  private  channels  thus  ascertained  at  any  time. 
In  PL  XIX  is  shown  the  type  of  distributary  head  used  on  the 
canals  of  the  Punjab.  On  the  Mutha  canals  in  Bombay  a  V- 
shaped  weir  is  placed  in  the  head  of  each  private  channel  or 
lateral  for  the  purpose  of  water  measurement,  while  a  water- 
cushion  is  built  in  the  lower  portion  of  the  distributary  head 
in  order  to  diminish  the  shock  of  the  falling  water.  The  rules 
for  the  dimensions  of  water-wells  or  cushions  are  about  the 
same  as  those  given  for  main  canals  (Article  138).  Distribu- 
taries are  passed  over  or  under  each  other  or  the  country  drain- 
age in  flumes  or  siphons  as  are  main  canals  (Chapter  XIV). 

203.  Iron  and  Steel  Distributary  Pipes. — Where  water  is 
conveyed  in  pipes  instead  of  open  channels,  these  are  gener- 
ally of  iron,  steel,  wood,  or  occasionally  of  cement.     The  iron 
or  steel  pipes  are  constructed    of  sheet   metal,  the  varieties 
being  spiral  riveted  pipe,  converse  lock-joined  kalamined  lap- 
welded  pipe,  and   straight  double-riveted   pipe.     The  dimen- 
sions of  these  distributary  pipes  range  from  6  to  30  inches  in 
diameter,  and  the  thickness    of  the  metal  is  trifling,  varying 
between  No.  8  and  No.  10  plate.     With  straight  riveted  pipe 
the  distance  apart  of  rivets  in  the  rows  ranges  from  1.33  to 
1.40  inches,  and  the  distance  between  any  two  rows  is  about  f 
of  an  inch.    This  wrought-iron  or  steel  pipe  is  invariably  coated 
with  hot  asphaltum  by  inserting  the  pipes  in  a  tank  of  refined 
asphaitum  fluxed  with  crude  oil  heated  nearly  to  burning  point. 
This  class  of   pipe   will   bear   pressures   of  from    100  to   200 
pounds  per  square  inch.     In  laying  it  air-valves  are  attached 
at  all  high  places,  and  an  air  standpipe  generally  at  the  highest 
point,  besides  which  blow-offs  are  placed  at  proper  intervals. 

204.  Wooden   Distributary   Pipes.  —  There   are   several 
types   of   patented  wood    pipe.     That  which  is   now  finding 
most  favor  is  the  invention  of  Mr.  C.  P.  Allen  of  Denver  and 
is  known  as  the  Colorado  wooden  pipe  (Fig.  56).     It  is  made 


202  t  DISTRIBUTARIES. 

of  varying  sizes  from  20  to  36  inches  in  diameter,  the  walls  of 
the  pipe  being  formed  of  longitudinal  staves  braced  together 
with  iron  or  steel  bands.  These  staves  are  shaped  on  the 
broad  sides  to  cylindrical  circles  and  the  edges  to  true  radial 
lines,  so  that  when  put  together  they  form  a  perfectly  cylin- 
drical pipe.  To  join  the  ends  of  the  staves,  a  thin  metallic 
tongue  is  inserted  which  is  a  trifle  longer  than  the  width  of 
the  stave  and  cuts  into  the  adjoining  ones.  The  confining 


FIG.  56.— COLORADO  WOODEN  PIPE. 


bands  are  of  round  or  flat  iron  or  steel  of  from  f  to  f  inches 
in  diameter  and  are  shipped  from  the  factory  as  rods,  provided 
at  one  end  with  a  square  head  and  at  the  other  with  a  thread 
and  nut.  They  are  bent  on  the  ground  on  a  bending-table 
and  coated  with  mineral  paint  or  asphalt  varnish,  and  are  cut 
about  6  inches  longer  than  the  outside  circumference  of  the 
pipe,  on  which  they  are  slipped  loose.  These  confining  bands 
are  placed  at  varying  distances  apart,  according  to  the  press- 
ure which  the  pipe  has  to  bear. 

205.  Rotation  in  Water  Distribution. — The  water  in  dis- 
tributaries can  be  most  economically  handled  if  a  system  of 
rotation  be  employed  in  admitting  it  to  the  heads  of  the 
private  channels.  It  is  more  convenient  and  economical  to 


ROTATION  IN    WATER  DISTRIBUTION.  2O3 

move  water  in  as  large  volumes  as  possible.  This  may  be 
done  by  regulating  the  amount  admitted  to  the  private  chan- 
nels and  the  periods  of  time  in  which  they  shall  receive  it. 
Thus  the  outlets  to  these  channels  may  be  closed  in  the  first 
length  of  the  canal  for  four  days,  in  the  second  for  three  days, 
and  so  on ;  and  then  this  order  may  be  reversed,  the  period  of 
rotation  being  such  as  to  change  the  length  of  closure  along 
the  various  portions  of  the  canal.  It  is  better  to  impose  these 
systems  of  rotation  on  long  portions  of  the  distributary  at 
once,  as  the  effect  in  forcing  the  water  down  to  the  tail  of  the 
distributary  is  then  more  noticeable.  Thus  if  a  distributary 
be  20  miles  in  length  and  all  the  outlets  in  the  first  5  miles  be 
closed,  those  in  the  second  5  miles  opened,  those  in  the  third 
5  miles  closed,  and  those  in  the  fourth  5  miles  opened  at  the 
same  time,  the  effect  will  be  to  produce  a  stronger  head  and 
to  carry  the  desired  amount  into  all  the  channels  in  the  last 
portion  of  the  canal ;  then  for  a  period  of  a  few  days  this  order 
may  be  reversed  and  without  difficulty  the  maximum  duty 
obtained  from  the  water  in  the  distributary.  To  make  this 
system  effective  rules  should  be  made  compelling  irrigators  to 
accept  water  when  their  irrigation  heads  are  open,  and  refusing 
it  to  them  when  their  turn  has  gone  by. 


CHAPTER   XVI. 
APPLICATION   OF  WATER,   AND    PIPE   IRRIGATION. 

206.  Methods  of  Applying  Water. — The  cultivator  ap- 
plies water  to  the  crops  by  various  methods,  depending  chiefly 
on  the  nature  of  the  crop  and  the  slope  of  the  surface  of  the 
ground.  These  methods  are  : 

1.  By  absorption  from  water  sprinkled  over  the  surface. 

2.  By  filtration  of  a  sheet  of  water  downward  through  the 
surface  of  the  soil. 

3.  By  lateral  percolation  from  an  adjacent  source  of  sup- 
ply. 

4.  By  absorption  from  a  subsurface  supply. 

The  first  method  includes  irrigation  by  nature  in  the  form 
of  rain,  or  by  sprinkling  with  a  watering-pot  or  hose.  This 
method  is  of  such  simple  character  as  to  require  no  further 
consideration  here. 

The  second  method  of  irrigation  is  called  flooding,  and  is 
accomplished  in  three  ways,  depending  on  the  character  of  the 
crop  and  on  the  slope  of  the  soil : 

1.  Flooding   of   meadows   by  simply  conducting   a   ditch 
along  the  upper  slope  of  the  land  and  allowing  the  water  to 
flow  from  this  completely  over  the  meadow. 

2.  Flooding  by  checks,  by  dividing  gently  sloping  surfaces 
into  level  benches  by  means  of  check  levees  and  permitting 
the  water  to  stand  in  these  as  in  still  ponds. 

3.  Flooding  by  the  checkerboard  system,  by  dividing  nearly 
level  ground  into  squares  by  surrounding  levees  and  allowing 
the  water  to  stand  in  these. 

The  third  method  of  application  is  generally  called  the 
furrow  method  and  is  accomplished  in  four  ways : 

I.  By  running  small  ditches  close  to  fruit-trees  and  vines, 
and  allowing  the  percolation  from  these  to  moisten  their  roots. 

204 


SIDE  HILL   FLOODING   OF  MEADOWS. 


205 


2.  By  letting  a  large  number  of  small  streams  flow  from 
flumes"  through    ditches    between    fruit-trees   and   vines,   and 
allowing  the  water  to  percolate  from  these  to  their  roots. 

3.  By  flowing  the  water  in  small  streams  through  the  fur- 
rows between  such  crops  as  potatoes  and  corn,  and  thus  grad- 
ually moistening  them. 

4.  By  drilling  grain  in  rows  or  shallow  furrows  and  running 
the  water  through  these.     This  is  practically  a  combination  of 
flooding  and  sidewise  soakage. 

The  fourth  method  of  irrigation  is  conducted  by  laying  pipes 
underground  and  having  outlets  in  these  under  each  fruit  tree  ; 
or  by  so  placing  these  outlets  that  the  water  escaping  there- 
from shall  moisten  the  roots  of  vines  and  trees  near  by. 

207.  Sidehill  Flooding  of  Meadows. — This  method  is  the 
most  wasteful  of  water,  but  it  is  that  most  commonly  practised 


FIG.  57.— DIAGRAM  ILLUSTRATING  FLOODING  OF  MEADOWS. 

in  the  cultivation  of  grass  and  cereals.     Wild  meadow  lands 
and  hayfields  are  flooded  by  simply  turning  the  water  on  them 


2O6     APPLICATION   OF    WATER,  AND   PIPE  IRRIGATION. 

when  the  slope  of  the  ground  is  sufficient  and  allowing  it  to  sink 
into  the  soil.  To  accomplish  this  the  water  is  made  to  enter  the 
field  at  its  highest  point  in  a  ditch  conducted  around  an  upper 
contour  of  the  field.  Breaks  are  made  at  intervals  in  the  side 
of  the  ditch,  and  the  water  being  allowed  to  flow  through  these, 
finds  its  way  in  a  thin  sheet  over  the  field  (Fig.  57).  This 
method  is  very  expensive  of  water  and  can  be  employed  on  but 
few  soils,  since  clayey  soils  bake  or  parch,  forming  a  thin  crust 
which  kills  the  growth  of  plants.  Instead  of  making  breaks 
in  the  side  of  the  ditches  checks  are  sometimes  formed  by 
little  dams  of  earth  or  wood. 

208.  Flooding  by  Checks. — This  method  consists  in  run- 
ning check  levees  around  the  slope  of  the  land  on  contour 
lines.  These  are  low  ridges  of  earth  about  I  foot  in  height, 
turned  up  with  a  plough  or  scraper  and  placed  at  such  distances 
apart  that  the  crest  of  each  shall  be  on  a  level  with  the  base  of 
the  check  above  it  (Fig.  58).  If  properly  built  these  checks 


CROSS      SECTION      Oft    a-b 

a  & 


FIG.  58. — IRRIGATION  BY  SYSTEM  OF  CHECK-LEVEES. 

will  last  for  many  years,  and  the  field  may  be  ploughed  and  re- 
ploughed  without  injury  to  them  or  their  in  any  way  affecting 
the  handling  of  the  crops.  In  comparatively  level  country  like 


FLOODING  BY  CHECKERBOARD   SYSTEM   OF  SQUARES.     2O? 
i 

that  in  Kern  county,  California,  the  distributary  ditches  are 
placed  as  much  as  a  quarter  of  a  mile  apart,  their  banks  form- 
ing two  of  the  bounding  ridges  or  levees,  the  third  or  lower 
boundary  being  a  contour  levee  connecting  the  ditch  banks. 
The  less  the  height  of  this  levee  the  better,  because  the  quan- 
tity of  water  spread  over  the  land  will  be  of  more  uniform  depth 
and  will  interfere  less  with  ploughing  and  harvesting;  the 
greater  the  width  of  the  levee  base  the  better.  From  6  to  12 
inches  is  the  best  height  and  from  15  to  20  feet  the  best  width 
of  base.  In  such  country  as  that  described  the  checks  range 
from  10  to  50  acres  each  in  area  and  require  from  12  to  20  miles 
of  levee  per  square  mile  of  check,  while  a  mile  of  levee  contains 
about  3000  cubic  yards  of  earth.  The  water  is  run  through  the 
ditches  (Fig.  58)  and  admitted  by  gates  into  each  separate 
check.  When  the  latter  is  full  the  water  is  drawn  off  to  the 
next  lower  level,  or  if  the  soil  is  porous  it  is  allowed  to  stand 
until  it  has  been  absorbed. 

209.  Flooding  by  Checkerboard  System  of  Squares.— 
This  method  is  practised  extensively  on  the  level  plains  of 
Southern  Arizona  and  in  India.  The  fields  are  divided  into 
squares  of  from  20  to  60  feet  on  each  sicje  (Fig.  59),  and  these 
are  separated  by  ridges  or  levees  of  from  10  to  12  inches  in 
height  from  which  openings  are  made  leading  from  one  square 
to  the  other.  In  some  cases  the  fields  are  divided  into  much 
larger  squares,  often  of  an  acre  in  extent,  depending  on  the 
slope  of  the  ground.  Again,  especially  in  India,  very  small 
squares  are  employed,  and  the  height  of  the  dividing  ridges  is 
made  as  low  as  6  inches,  so  that  these  do  not  interfere  materi- 
ally with  the  harvesting  and  ploughing  of  the  fields.  The  chief 
objection  to  this  method  is  the  obstruction  created  by  the 
check  levees.  When  these  can  be  placed  far  enough  apart  they 
interfere  but  little  with  the  operations  of  the  cultivator:  other- 
wise he  must  use  spade  and  hoe  instead  of  plough. 

Water  is  admitted  to  one  square  at  a  time  and  is  either 
permitted  to  soak  into  the  soil  or  is  drawn  off  to  be  used  in 
the  next  square  below,  much  as  in  the  check  method.  The 
chief  crops  irrigated  by  this  method  are  hay,  grain,  and  vege- 


208     APPLICATION  OF    WATER,  AND  PIPE   IRRIGATION. 


tables.  Where  flooding  is  practised  by  checks  or  squares,  any- 
where from  4  to  12  inches  in  depth  of  water  is  let  on  at  a 
single  watering.  The  number  of  these  waterings  may  range 
between  two  and  five  in  a  season,  according  to  the  crop,  soil, 
and  climate.  Rice  and  sugar  cane  are  irrigated  in  India  and 


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Cross    Section  on      a  -  h. 


FIG.  59. — FLOODING  BY  SYSTEM  OF  SQUARES. 

South  America  by  squares.  These  crops  require  a  very  large 
amount  of  water,  and  as  a  consequence  the  height  of  the  levees 
is  rarely  less  than  a  foot  and  is  often  greater.  These  are  filled 
with  water  and  it  is  allowed  to  stand  on  them  for  long  periods 
of  time,  the  soil  being  seldom  permitted  to  dry. 

210.  Flooding  by  Terraces. — This  method  is  employed 
chiefly  in  India  and  China,  and  has  recently  been  adopted  on  a 
small  scale  in  the  neighborhood  of  Newcastle,  California.  It 


FURRbW  IRRIGATION  OF    VEGETABLES  AND    GRAIN.     2OQ 

consists  of  laying  out  steeply  sloping  sidehill  ground  in  terraces, 
the  lower  sides  of  which  are  surrounded  by  high  levees.  These 
are  practically  exaggerated  forms  of  checks,  and  as  employed 
in  California  are  maintained  and  operated  on  the  sa:"2  general 
principle,  though  they  receive  a  large  proportion  of  their  water 
supply  from  the  drainage  of  the  hillsides  above.  As  employed 
in  india  or  China,  these  terraces  also  receive  their  water  supply 
chiefly  from  the  drainage  above,  and  hold  it  as  in  a  small  tank 
or  reservoir  of  a  few  feet  in  depth.  As  the  water  soaks  into 
the  soil  of  the  terrace,  rice  or  similar  crops  are  sown,  and  the 
amount  of  moisture  retained  in  the  earth  by  such  a  volume  of 
water  entering  it  is  sufficient,  with  the  addition  of  what  may 
be  received  from  occasional  rains,  to  irrigate  the  crops. 

211.  Furrow  Irrigation  of  Vegetables  and  Grain. — This 
method  is  practised  by  laying  the  field  off  in  shallow  ditches 
run  around  its  upper  slope.  From  these  ordinary  plough  or  V-- 
shaped furrows  radiate  down  the  slope  of  the  field,  and  between 


FIG.  60.— FURROW  IRRIGATION  OF  GRAIN. 


these  the  vegetables,  potatoes,  or  grain  are  planted.  Where  the 
country  slopes  more  irregularly  or  steeply  the  furrows  are  run  at 
various  angles  down  the  slope  in  such  manner  that  their  grade 
shall  not  be  too  steep.  The  water  is  then  turned  into  a  few  of 
these  furrows  at  a  time  by  blocking  the  ditch  above  with  a  clod 


2IO     APPLICATION   OF    WATER,  AND   PIPE   IRRIGATION. 

of  dirt  or  a  board  (Fig.  60),  and  the  water  penetrates  by  sidewise 
soakage  to  the  crops.  Corn  is  irrigated  by  the  furrow  method 
by  ploughing  a  ditch  along  the  upper  slope  of  the  field  as  above 
described,  and  by  drilling  the  grain  down  the  slope  of  the  field 
radially  from  this  ditch  and  permitting  the  water  to  enter  a  few 
of  the  drill  rows  at  a  time.  Grain  fields  are  sometimes  pre- 
pared for  this  method  of  combined  flooding  and  furrow  irriga- 
tion by  roiling  the  field  after  the  grain  is  planted  with  a  heavy 
roller  on  the  surface  of  which  are  angular  projections  of  from 
~J  to  I  foot  apart  and  a  few  inches  in  height.  These  make 
grooves  in  the  surface  of  the  soil  in  a  direction  parallel  to  the 
^lope,  and  the  water  is  admitted  to  these  and  permitted  to  flow 
through  them  as  in  the  case  of  ploughed  furrows  or  drill  rows. 
212.  Combined  Flooding  and  Furrow  Irrigation  of  Or- 
•chards. — Where  orchards  are  directly  flooded  the  tendency 
..of  the  water  is  to  bring  the  roots  to  the  surface  and  thus  en- 
feeble them.  To  prevent  this  furrows  are  run  from  the  upper 


FIG.  61. — FURROW  IRRIGATION  OF  ORCHARDS. 


ditches,  generally  in  a  double  row,  one  on  either  side  of  and 
at  a  short  distance  from  the  trees  or  vines  (Fig.  61).  By 
this  means  the  water  percolates  into  the  soil  and  reaches  the 
roots  of  the  tree  by  sidewise  soakage  at  some  depth  beneath 


IRRIGATING   ORCHARDS  BY  SMALL  FURROWS.          211 

the  surface,  thus  moistening  and  encouraging  their  growth. 
Another  method  of  flooding  orchards  is  to  protect  the  trees  by 
earth  ridges  thrown  up  so  as  to  prevent  the  water  from  reach- 
ing within  3  to  4  feet  of  them.  In  this  method  the  entire 
field  is  flooded  with  the  exception  only  of  the  areas  immedi- 
ately adjacent  to  the  trees.  This  practice  is  wasteful  of  water, 
as  much  more  is  employed  than  is  required.  Olive  and 
orange  trees  are  watered  from  three  to  four  times  in  a  season, 
vines  once  or  twice  and  often  not  at  all  after  the  first  few 
seasons. 

213.  Irrigating  Orchards  by  Small  Furrows.  —  This 
method  is  practised  as  yet  chiefly  in  the  neighborhood  of  San 
Bernardino  valley,  California.  The  principle  underlying  this 
method  is  that  the  ground  shall  be  put  in  the  condition  which 
it  would  be  in  after  several  days  of  long  soaking  rain,  rather 
than  in  the  condition  which  it  would  be  in  after  a  small 
cloud-burst,  which  is  the  condition  resulting  from  most  other 
methods  of  surface  irrigation.  This  is  done  not  by  running 
large  streams  of  water  through  the  furrows  for  a  short  period 
of  time,  but  by  running  small  streams  through  them  for  a  long 
time.  It  is  accomplished  (Fig.  61)  by  running  a  number  of 
ploughed  furrows  between  the  rows  of  trees,  the  nearest  furrow 
not  being  closer  than  3  feet  from  the  trees,  and  the  distance 
between  furrows  from  2  to  3  feet.  The  volume  of  each 
of  the  streams  running  through  these  does  not  exceed  one 
four-hundredth  of  a  second-foot,  and  the  water  is  run  through 
them  for  two  and  three  days  at  a  time.  Where  the  soil  is  not 
too  loose  or  sandy  this  method  seems  to  give  the  best  results 
for  fruits  and  vines  and  may  be  used  with  some  success  on 
grain  and  corn.  , 

In  order  that  the  method  shall  be  successful,  the  laterals 
from  which  the  furrows  are  filled  and  which  come  from  the 
main  distributary  must  have  a  uniform  depth  and  slope  to 
a  degree  which  cannot  be  secured  in  open  earth.  This  is 
accomplished  by  running  wooden  laterals  or  flumes  along  the 
surface  of  the  ground  down  its  slope.  These  simple  flumes 
are  but  a  few  inches  in  cross-sectional  area,  generally  the  width 


212     APPLICATION  OF    WATER,  AND  PIPE   IRRIGATION. 

of  a  plank  at  base  and  on  the  sides.  They  are  given  a  suffi- 
cient grade  to  produce  a  good  velocity  and  where  the  natural 
slope  is  too  great  falls  are  introduced.  The  water  escapes 
from  these  flumes  into  the  furrows  through  auger-holes  bored 
in  their  sides  opposite  each  furrow  and  on  a  level  with  the 
bottom  of  the  flume  (Fig.  61).  The  flow  through  these  holes 
is  regulated  by  wooden  buttons  or  plugs  which  are  inserted  in 
them.  For  small  orchards,  these  flumes  generally  have  a 
capacity  of  about  -J  a  second-foot.  Fruit  trees  thrive  well 
on  from  three  to  five  waterings  and  vines  on  from  two  to 
three  waterings  when  supplied  by  this  method. 

214.  Subsurface  Irrigation. — Irrigation  from  beneath  the 
surface,  or  sub-irrigation,  is  the  most  perfect  method  of  supply- 
ing water  to  plants.    The  idea  is  to  replace  soakage  from  above 
by  means  of  flooding  or  furrows,  by  absorption  from  below, 
which,  to  be   perfect,  should    not   wet   the    surface.     This   is 
effected  by  laying  pipes  underground,  and  these  derive  'their 
supply  from  distributaries  which  are  usually  sheet-iron  or  steel 
pipes.     While  the  cost  of  preparing  land  for  this  method  of 
irrigation  is  relatively  great,  it  is  more  than  repaid  by  the  sav- 
ing in  water  charges,  since  the  duty  of  water  is  great,  reaching 
from   500  to    1000  acres  per  second-foot.     This  method  has 
been    most    extensively  employed    among   the  valuable    fruit 
lands  of    Southern  California,  and  where  these  lands  are  di- 
vided into  and  sold  in  orchard  lots  of  from  10  to  20  acres  in 
area,  the  distributing  pipes  are  carried  to  the  highest  point  in 
each  one  of  these  lots,  and  from  this  the  sub-irrigation  pipes 
are  conducted  through  the  orchards. 

215.  Sub-irrigation  Pipes. — These  are  made  of  sheet-iron 
or  steel  or  of  some  porous  or  glazed  material,  the  former  being 
usually  a  combination  of  cement,  lime,  sand,  and  gravel,  with  a 
small  admixture  of  potash  and  linseed  oil,  and  are  known  as 
asbestine  pipes.     Glazed  earthenware  pipes  are  becoming  more 
popular  than  any  other  form.      Asphalt-concrete   pipes  have 
been   successfully   employed   for  sub-irrigation  and   have   the 
advantage  over  simple  concrete  pipes  of  being  impervious  to 
water.     These  are  united  by  heating  so  as  to  form  a  continu- 


SUB-IRRIGATION  PIPES.  213 

ous  pipe.  These  distributing  pipes  are  usually  made  in  various 
dimensions,  according  to  the  circumstances  under  which  they 
are  to  be  used  and  the  area  which  each  is  to  control.  In  some 
cases  they  are  as  small  as  2  inches  in  diameter,  and  from  this 
they  range  to  6  inches  where  the  principal  distributaries  are 
reached. 

216.  Method  of  Laying  Pipes. — Sub-irrigation  pipes  are 
laid  in  open  trenches  at  a  depth  of  I  to  \\  feet  below  the  sur- 
face, parallel  to  the  rows  of  trees  or  vines  in  the  orchard,  and 
the  trench  is  then  filled  in  with  earth.  A  method  has  been 
attempted  of  laying  the  pipes  by  means  of  machinery,  though 
as  yet  this  has  not  met  with  success.  Irrigation  is  effected 
from  these  pipes  sometimes  by  cutting  a  hole  on  the  upper 
side  and  inserting  therein  a  wooden  plug  opposite  each  tree  or 
vine.  Each  plug  is  surrounded  by  a  larger  standpipe  set 
loosely  on  top  of  the  distributary  pipe,  open  at  the  bottom 
and  reaching  to  the  surface  of  the  ground  for  the  purpose  of 
keeping  the  dirt  away  from  the  outlet  and  rendering  it  acces- 
sible at  all  times  for  inspection. 

The  process  of  irrigation  consists  in  simply  turning  the 
water  off  or  on  from  the  main  pipe,  when  it  finds  its  way 
through  the  outlets,  fills  the  standpipe,  and  slowly  percolates 
to  the  surface  of  the  ground.  One  of  the  great  objections  to 
the  use  of  pipes  for  sub-irrigation  is  the  necessity  for  having 
these  small  holes  or  openings  from  which  water  can  escape,  and 
the  resultant  danger  to  the  pipe  of  roots  growing  into  the  open- 
ings and  clogging  or  destroying  them.  If  muddy  water  is 
let  into  the  pipe  there  is  danger  of  clogging  unless  sufficient 
pressure  can  be  used  to  flush  them.  One  of  the  most  satisfac- 
tory methods  of  letting  the  water  escape  consists  in  cutting 
a  section  several  inches  in  length  out  of  the  continuous  pipe 
where  the  plug-hole  should  be  inserted,  and  by  replacing  it  by  a 
U-shaped  shoe  placed  below  the  cut  in  the  pipe.  A  tile  a  little 
longer  than  the  gap  covers  it  and  water  escapes  between  the 
two  surfaces.  By  this  method  of  irrigation  plants  do  not  re- 
ceive the  fertilizing  elements  brought  to  them  by  the  sediment 
carried  in  surface  waters.  On  the  other  hand,  the  pipes  have 


214     APPLICATION  OF    WATER,    AND   PIPE   IRRIGATION. 


the  advantage  of  acting  as  drains  to  carry  off  surplus  water 
and  thus  prevent  the  rise  of  alkali  and  other  evils  attend- 
ing supersaturation,  especially  as  the  water,  when  properly 
handled,  does  not  reach  the  surface  and  evaporate  there. 

217.  Measuring  Sub-irrigation  Waters. — In  the  Ales- 
sandro  district  in  California  a  water-measuring  apparatus  is  em- 
ployed which  consists  of  a  4-inch  iron  standpipe  resting  on  the 
6-inch  vitrified  service-pipe  (Fig.  62).  At  the  top  of  the  stand- 


FIG.  62. — ALESSANDRO  HYDRANT. 

pipe  a  scale  is  so  arranged  that  the  amount  of  water  flowing 
through  can  be  measured  by  simply  reading  it.  A  valve  inside 
the  standpipe,  which  can  be  locked  by  a  simple  device,  is  oper- 
ated by  a  screw  attachment  and  admits  the  proper  amount  of 
water.  On  the  outer  surface  of  the  standpipe  is  a  pressure- 
gauge  which  shows  the  head  of  water  on  the  measuring-slot. 
The  unit  of  measure  used  on  these  pipes  is  the  miner's  inch. 
This  device  has  met  with  some  favor,  but  is  open  to  the 
same  objection  as  all  similar  water  meters,  namely,  that  it  is 
expensive  and  troublesome,  requiring  much  attention  for  its 
proper  management. 


WORKS   OF  REFERENCE. 

218.  Works  of  Reference.    Canals  and  Canal  Works. — 

BAROIS,  J.  Irrigation  in  Egypt.  Paris,  1887.  Translated  by  Major 
A.  M.  Miller,  U.S.A.  War  Department,  Washington,  D.  C. 

BIRCHA.  Distribution  of  Water  from  Irrigation  Canals.  Proc.  Inst. 
C.  E.,vol.  72.  London,  1882. 

BUCKLEY,  ROBERT  B.  Keeping  Irrigation  Canals  Clear  of  Silt.  Proc. 
Inst.  C.  E.,  vol.  58,  Part  IV.  London,  1879. 

Movable  Dams  in    Indian  Weirs.     Proc.    Inst.  C.   E.,  vol.  60, 

Part  II.     London,  1880. 

CAUTLEY,  COL.  SIR  PROBY  T.    Ganges  Canal  Works.    3  vols.    London, 

1860. 
DERRY,  J.  D.     Victoria  Royal  Commission  on  Water  Supply.     Fourth 

Progress  Report.     Melbourne,  1885. 
FLYNN,  P.  J.     Irrigation    Canals   and   other    Irrigation   Works.     San 

Francisco,  Cal.,  1892. 
HALL,  WM.  HAM.     Report  of  the  State  Engineer  to  the  Legislature  of 

California.     Part  IV.      Sacramento,  Cal.,  1881. 

Irrigation  in  Southern  California.     Sacramento,  Cal.,  1888. 

HERSCHEL,  CLEMENS.     The  Holyoke  Dam.     Trans.  Am.  Soc.  C.  E., 

vol.  12.     New  York. 
LEVINGE,  H.  C.     Soane  Canal.     Professional  Papers,  VII.     Roorkee, 

India,  1870. 
MONCRIEFF,  COLIN  C.  SCOTT.     Irrigation  in    Southern  Europe.     E.  & 

F.  N.  Spon,  London,  1868. 
MULLIN,  LiEUT.-GEN.   J.     Irrigation  Manual.     E.  &  F.  N.  Spon,  New 

York  and  London,  1890. 
MEDLEY,  LIEUT.-COL.  J.  G.     Manual  of  Irrigation  Works.     Thomason 

Civil  Engineering  (College,  Roorkee,  India,  1873. 
NAVIGATION  DE  LA  SEINE,   Exposition  Universelle   Internationale  de 

1889,  Paris.     Imprimerie  Nationale,  Paris,  1889. 

RONNA,  A.     Les  Irrigations.'     Firmin-DidotetCie.     2  vols.     Paris,  1889. 
SCOTT,   JOHN.     Irrigation    and  Water  Supply.     Crosby,  Lockwood   & 

Co.,  London,  1883. 
STEWART,  HENRY.     Irrigation   for   the   Farm,  Garden,  and   Orchard. 

Orange  Judd  Co.,  New  York,  1889. 
VERNON-HARCOURT,  T.  F.     Fixed  and  Movable  Weirs.     Proc.  Inst. 

C.  E.,  vol.  60,  Part  II.     London,  1880. 
WEISBACH,  P.  J.,  and   Du  Bois,  A.   JAY.     Hydraulics  and  Hydraulic 

Motors.     John  Wiley  &  Sons,  New  York,  1889. 

WHITING,  J.  E.     The  Nira  Canal.     Proc.  Inst.  C.  E.,  vol.  77,  p.  423. 
WILCOX,  W.     Egyptian  Irrigation.     E.  &  F.  N.  Spon,  London  and  New 

York,  1889. 
WILSON,  H.  M.     Irrigation  in  India.     Twelfth   Annual  Report  U.  S. 

Geological  Survey,  Part  II.     Washington,  D.  C.,  1891. 


PART   III. 

STORAGE  RESERVOIRS. 


CHAPTER   XVII. 
LOCATION  AND   CAPACITY   OF   RESERVOIRS. 

219.  Classes  of  Storage  Works. — A  storage  work  is  any 
variety  of  natural  or  artificial  impounding  reservoir  or  tank  for 
the  saving  of  superfluous  or  flood  waters.     Storage  works  are 
employed  to  insure  a  constant  supply  of  water  during  each  and 
every  season  regardless  of  the  amount  of  rainfall.     They  may  be 
classified  according  to  the  character  and  location  of  the  storage 
basin,  or  the  design  and  construction  of  the  retaining  wall  or 
dam  which  closes  it.     Under  the  former  classification  are: 

1.  Natural  lake  basins; 

2.  Reservoir  sites  on  natural  drainage  lines,  as  a  valley  or 
canyon  through  which  a  stream  flows ; 

3.  Reservoir  sites  in  depressions  on  bench  lands  ; 

4.  Reservoir  sites  which  are  in  part  or  wholly  constructed 
by  artificial  methods. 

Under  the  second  classification  are: 

1.  Earth  dams  or  embankments; 

2.  Combined  earth  and  loose-rock  dams  ; 

3.  Hydraulic-mining  type  of  dam,  or  dams  constructed  of 
loose  rock  or  loose  rock  and  timber ; 

4.  Combined  loose-rock  and  masonry  dams  ; 

5.  Masonry  dams. 

220.  Relation  of  Reservoir  Site  to  Land  and  Water 
Supply. — There  are  several  modifying  considerations  affecting 

216 


RESERVOIR   SITES.  2 1/ 

the  value  of  the  reservoir  site.     Among  the  more  important  of 
these  are : 

1.  The  relation  of  the  site  to  the  irrigable  lands ; 

2.  The  relation  of  the  site  to  its  catchment  basin  or  source 
of  supply ; 

3.  The  topography  of  the  site  ; 

4.  The  geology  of  the  site. 

The  cost  of  water  storage  depends  chiefly  on  the  last  two, 
while  the  value  of  the  site  for  storing  water  and  the  possibility 
of  filling  the  reservoir  depends  on  the  first  two. 

In  considering  the  relation  of  the  reservoir  site  to  the  irri- 
gable lands,  the  former  should  be  situated  at  a  sufficient  alti- 
tude above  the  latter  to  allow  of  the  delivery  of  water  to  them 
by  natural  flow.  The  area  of  these  lands  should  be  sufficient 
to  require  the  entire  amount  of  water  stored,  that  the  maximum 
return  may  be  derived  from  water  rates,  and  the  reservoir 
should  be  as  near  as  possible  to  the  irrigable  lands  in  order 
that  the  loss  in  transportation  shall  be  a  minimum.  It  not 
infrequently  happens,  however,  that  the  reservoir  is  of  neces- 
sity located  at  some  distance  from  the  irrigable  lands,  thus 
requiring  either  a  long  supply  canal  or  that  the  water  be 
turned  back  into  the  natural  drainage  channel,  down  which  it 
will  flow  till  diverted  in  the  neighborhood  of  the  irrigable  lands. 
This  is  very  wasteful  of  water,  since  the  losses  by  absorption, 
percolation,  and  evaporation  are  great,  especially  if  the  bed  of 
a  natural  channel  is  used  as  a  portion  of  the  supply  line. 

As  related  to  the  source  of  supply,  the  reservoir  site  may 
be  on  a  perennial  stream  the  discharge  of  which  is  more  than 
sufficient  to  fill  it,  in  which  case  the  supply  is  assured.  It  may 
be  on  a  stream  the  available  perennial  discharge  of  which  is 
sufficient  to  fill  it  in  times  of  flood.  It  may  be  on  an  intermit- 
tent stream  subject  to  occasional  flood  discharges  of  sufficient 
volume  to  fill  the  reservoir  so  as  to  enable  it  to  tide  over  a  couple 
of  seasons  of  moderate  supply.  Or  the  reservoir  site  may  be 
situated  above  and  away  from  any  natural  drainage  line,  in 
which  case  it  will  receive  its  supply  either  by  a  canal  diverted 
from  some  perennial  stream  or  from  artesian  wells  or  springs. 


218  LOCATION  AND   CAPACITY  OF  RESERVOIRS. 

221.  Character  of  Reservoir  Site. — If  situated  in  a  natu- 
ral lake  basin,  a  short  drainage  cut  or  a  comparatively  cheap 
dam  or  both  may  give  a  large  available  storage  capacity.     Such 
sites  are  usually  the  best  and  cheapest,  costing  for  construction 
as  low  as  20  cents  per  acre-foot  stored,  and  in  unfavorable  cases 
rarely  exceeding  $3  per  acre-foot.     The  most  abundant  reser- 
voir sites  are  those  on   natural  drainage  lines,  though   these 
are  usually  the  most  expensive  of  construction  owing  to  the 
precautions  which  it  is  necessary  to  take  in  building  the  dam 
to  provide  for  the  discharge  of  flood  water.     Almost  equally 
abundant  are  those  reservoir  sites  found  in  alkaline  basins  or 
depressions  on  bench  or  plain  lands,  especially  on  the  plains 
sloping  to  the  eastward  of  the  main  Rocky  mountains  and  in 
the  foothills  of  the  Sierras  in  California.     The  utilization  of 
such   basins  as   reservoir  sites   is  comparatively  inexpensive; 
they  can  be  converted  into  reservoirs  by  the  construction  of  a 
deep  drainage  cut  or  of  a  comparatively  cheap  earth  embank- 
ment.    Scarcely  any  provision  is  necessary  for  the  passage  of 
floods.     The  heaviest  item  of  expense  in  connection  with  these 
sites  is  the  supply  canal  for  filling  them  from  some  adjacent 
source. 

Artificial  reservoirs  are  occasionally  constructed  where 
water  is  valuable,  by  the  erection  of  an  earth  embankment 
above  the  general  surface  of  the  country  or  by  the  excavation 
of  a  reservoir  basin  by  artificial  means.  Such  constructions  are 
usually  insignificant  in  dimensions,  as  the  expense  of  building 
large  reservoirs  of  this  kind  would  ordinarily  be  prohibitive. 
Shallow  reservoirs  should  not  be  constructed.  The  loss  from 
evaporation  and  percolation  is  proportionately  great,  and  the 
growth  of  weeds  is  encouraged  where  the  depth  is  less  than 
seven  feet,  by  the  sunlight  penetrating  to  the  bottom. 

222.  Topography  and    Survey  of   Reservoir    Sites.— 
Knowing  the  position  of  the  irrigable  lands,  a  careful  prelimi- 
nary survey  should  be  made  of  the  entire  neighborhood  to  dis- 
cover all  possible  reservoir  sites,  and  the  outlines  of  the  catch- 
ment basins  of  each  of  these  should  be  mapped,  while  stream 
gauging  should  be  conducted  and  examinations  and  inquiries 


TOPOGRAPHY  AND  GEOLOGY  OF  RESERVOIR  SITES.     219 

made  to  ascertain  the  minimum  discharge  of  the  streams 
and  their  flood  heights,  as  well  as  the  amount  of  evaporation 
and  percolation  (Chapters  III  and  IV).  Having  determined 
in  a  general  way  upon  the  location  of  the  reservoir  site,  a 
detailed  survey  of  it  should  be  made.  This  can  ordinarily  be 
best  done  by  means  of  a  plane  table.  The  highest  possible 
point  to  which  the  dam  may  reach  may  be  taken  as  a  basis 
and  a  top  contour  run  out  closing  around  the  entire  site.  In 
addition  to  this  a  main  traverse  should  be  run  through  the 
central  or  lowest  line  of  the  site  from  the  dam  to  the  extreme 
end  where  it  will  connect  with  the  top  contour.  Cross-section 
lines  may  be  run  from  this  with  the  plane  table,  and  the  topog- 
raphy of  the  site  sketched  in  5-foot  contours  and  plotted  to  some 
large  scale,  preferably  500  to  1000  feet  to  the  inch.  Where  the 
country  is  open  and  unobstructed  by  timber  the  site  may  be 
triangulated  from  one  side,  as  a  check  on  the  cross-section  lines, 
and  where  the  slopes  are  even  these  may  be  best  determined 
by  means  of  gradienter  lines  run  up  and  down  them  from  a 
base  contour.  Such  a  map  will  enable  the  engineer  to  deter- 
mine the  capacity  of  the  reservoir  for  various  depths  of  water. 

The  dam  site  should  be  surveyed  in  greater  detail,  several 
possible  sites  being  cross-sectioned  and  mapped  in  i-foot  con- 
tours and  at  a  scale  of  perhaps  100  feet  to  the  inch.  This 
work  should  be  done  with  transit  and  chain,  whereas  in  the  reser- 
voir survey  the -stadia  may  be  satisfactorily  employed  on  most 
of  the  cross-section  lines.  With  such  a  knowledge  of  the  topog- 
raphy of  a  catchment  basin  and  of  the  reservoir  and  dam  sites 
as  the  resulting  map  will  give,  the  engineer  may  readily  com- 
pute the  cost  of  construction  of  dams  for  various  heights  as 
well  as  the  contents  of  the  reservoir  for  these  heights,  and  thus 
determine  what  height  of  dam  will  be  most  economic  of  con- 
struction, for  there  is  always  some  height  which  will  render  the 
cost  of  storage  a  minimum. 

223.  Geology  of  Reservoir  Sites. — Having  ascertained 
the  desirability  of  the  reservoir  site  topographically  and  hydro- 
graphically,  a  few  test  borings  or  trial  pits  should  be  sunk  at 
various  points  on  the  reservoir  basin,  and  especially  at  the  dam 


220 


LOCATION  AND    CAPACITY  OF  RESERVOIRS. 


site,  to  ascertain  the  character  of  the  soil  and  the  dip  of  the 
strata  underlying  the  proposed  reservoir.  The  geological  con- 
formation may  be  such  as  to  contribute  to  the  efficiency  of  the 
reservoir,  or  it  may  prove  so  unfavorable  as  to  be  irremediable 
by  engineering  skill.  A  reservoir  site  which  is  situated  in  a 
synclinal  valley  as  shown  in  A,  Fig.  63,  is  the  most  favorable. 


FIG.  63. — DIAGRAMS  ILLUSTRATING  GEOLOGY  OF  RESERVOIR  SITE. 

In  this  the  strata  incline  from  the  hills  towards  the  lower  lines 
of  the  valley,  and  any  water  which  may  fall  on  to  these  hills 
will  find  its  way  by  percolation  through  the  strata  into  the 
reservoir,  thus  adding  to  its  volume.  An  anticlinal  valley 
is  the  least  favorable  for  a  reservoir  site  (Fig.  63,  B).  In  such 
a  valley  as  this  the  strata  dip  away  from  the  reservoir  site  and 
would  permit  of  the  escape  of  much  of  the  impounded  water, 
percolation  through  the  strata  leading  it  off  to  adjoining 
valleys.  A  class  of  geological  formation  intermediate  between 
these  two  is  that  represented  in  C,  Fig.  63,  in  which  the  valley 
has  been  eroded  in  the  side  of  strata  which  dip  in  one  direc- 
tion. Here  the  upper  strata  lead  water  from  the  adjoining 


COST  AND  DIMENSIONS  OF  STORAGE   RESERVOIRS.   221 


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222  LOCATION  AND   CAPACITY  OF  RESERVOIRS. 

hills  into  the  reservoir,  while  the  strata  on  the  lower  side  tend 
to  carry  it  off  from  the  reservoir  by  percolation.  In  such  a 
case  it  is  probable  that  the  reservoir  would  neither  gain  nor  lose. 

If  the  surface  proposed  reservoir  site  is  composed  of  a  deep 
bed  of  coarse  gravel  or  sand  or  even  limestone,  crevices  in  the 
latter  or  between  the  interstices  of  the  former  will  tend  greatly 
to  diminish  the  capacity  of  the  reservoir  by  seepage  from  it. 
Again,  the  geologic  formation  may  be  most  unfavorable,  yet  if 
the  surface  of  the  reservoir  site  be  covered  with  a  deep  deposit 
of  alluvial  sediment  or  of  clay  or  dirty  gravel  or  other  equally 
impervious  material,  little  danger  may  be  apprehended  from 
loss  by  seepage. 

224.  Cost  and  Dimensions  of  some  Great  Storage 
Reservoirs. — In  Table  XI  are  given  the  capacities,  material, 
dimensions  of  dam,  and  cost  per  acre-foot  stored  of  some  of 
the  great  storage  reservoirs  which  are  used  for  purposes  of 
irrigation. 


CHAPTER  XVIII. 
EARTH  AND   LOOSE-ROCK  DAMS. 

225.  Earth  Dams  or  Embankments. — The  choice  of  t*he 
material  of  which  the  dam  shall  be  constructed,  whether  it  shall 
be  of  earth,  masonry,  or  loose  rock,  is  dependent  largely  upon 
the  character  of  the  foundation  and  the  cost  of  transportation. 
Earth  dams  when  well  constructed  are  fully  as  substantial  as 
those  of  masonry,  and  in  many  cases  they  are  far  more  so.  In 
countries  subject  to  earthquakes,  or  where  the  rock  foundation 
is  not  thoroughly  homogeneous,  an  earth  dam  is  decidedly 
preferable  to  one  of  masonry.  They  are  usually  cheaper,  and 
where  transportation  is  expensive  they  are  very  much  cheaper. 
Providing  a  substantial  and  abundant  wasteway  of  a  sufficient 
capacity  to  carry  the  greatest  possible  flood  be  provided,  an 
earth  dam  is  generally  to  be  preferred  in  mild,  damp  climates. 
In  warm,  dry  climates  they  are  liable  to  dry  and  crack.-  For 
reservoirs  over  100  feet  in  depth  masonry  dams  are  to  be  pre- 
ferred, as  earth  dams  are  nearly  as  expensive  when  transporta- 
tion is  cheap,  and  are  more  liable  to  be  badly  built. 

As  before  stated,  the  choice  between  the  two  depends 
largely  on  the  foundation.  A  substantial  masonry  dam  can- 
not be  founded  on  loose  gravel  or  soil ;  an  earth  dam  should 
rarely  be  founded  on  rock,  owing  to  the  difficulty  of  making  a 
tight  joint  between  it  and  the  earth.  There  are  three  general 
types  of  earth  dams: 

1.  Earth  dams  having  a  central  core  or  wall  of  puddled 
earth  ; 

2.  Earth  dams  having  a  central  core  of  masonry  or  wood  ; 

3.  Earth  dams  built  up  in  layers  of  homogeneous  material, 
without  central  core  or  puddle  facing. 

223 


224  EARTH  AND   LOOSE-ROCK  DAMS. 

226.  Dimensions  of  Earth  Dams. — An  earth  dam  may  be 
supposed  to  fail  in  two  ways,  either  by  yielding  to  the  hori- 
zontal pressure  of  the  water  overturning  it,  or  by  sliding  on  its 
base.  The  simplest  form  of  calculation  clearly  demonstrates 
what  is  fully  acknowledged  by  all  engineers,  namely,  that  the 
dam  will  not  be  destroyed  by  overturning  or  revolving  about 
its  lower  toe  ;  hence  the  only  theory  as  to  its  destruction  is  that 
it  may  slide  on  its  base.  The  conditions  of  stability  will  be 
satisfactory  when  the  horizontal  component  of  the  water  press- 
ure against  the  bank  equals  the  weight  of  the  latter  plus  the 
vertical  pressure  exercised  by  the  water  to  hold  it  down,  and 
multiplied  by  the  coefficient  of  friction.  Such  a  case  is  rarely 
or  never  apt  to  occur.  In  point  of  fact  such  structures  usually 
fail,  not  by  overturning  or  sliding  on  their  bases,  but  by  the 
disintegration  of  their  particles  due  to  the  percolation  of  water. 

When  subjected  to  the  contact  of  water  earth  loses  a  cer- 
tain amount  of  its  stability,  and  therefore  it  is  customary  to 
give  the  inner  slope  of  an  embankment  a  greater  inclination 
than  the  outer  slope.  These  slopes  depend  on  the  character 
of  the  material,  When  the  outer  slope  will  stand  with  an  in- 
clination  of  I  on  2\  the  inner  slope  should  be  I  on  3. 

The  interior  and  exterior  slopes  of  earth  dams  may  be  con- 
sidered  as  planes  forming  together  an  angle  of  not  less  than 
90  degrees,  and  the  figure  should  be  so  formed  in  order  to  in- 
crease its  stability,  that  lines  of  pressure  passing  from  the 
interior  faces  at  right  angles  may  fall  within  its  base.  As  one 
cubic  foot  of  rammed  earth  weighs  about  100  pounds  and  a 
cubic  foot  of  water  62^  pounds,  we  find  the  base  of  a  prism 
resisting  the  lateral  thrust  of  the  water  does  not  require  to  be 
more  than  two  thirds  of  the  depth  of  the  column  it  supports. 
Hence  all  quantities  above  that  are  due  to  the  natural  slopes, 
the  stability  of  the  dam,  and  the  prevention  of  percolation. 

In  large  works  it  is  frequently  a  matter  of  close  calculation  to 
determine  which  will  be  the  more  economical, — dams  exclusively 
of  earth  or  those  whose  inner  slopes  are  supported  by  retaining 
walls  of  masonry.  The  outer  slope  of  the  dam  may  vary  be- 
tween I  on  i-J  and  I  on  3^,  according  to  the  character  of  the 


DIMENSIONS   OF  EARTH  DAM  S—  FOUNDATIONS,         22$ 

material.  Light  sand  requires  the  flattest  slope.  A  firm  mix- 
ture of  gravel  and  clay  will  stand  a  slope  of  about  I  on  i£. 
The  inner  slope  of  the  darn  should  be  about  £  on  I  greater  than 
the  outer  slope.  It  is  not  unusual,  as  in  the  case  of  the  Ashti 
dam  (PI.  XX),  to  make  the  inner  slope  near  the  top  a  little 
steeper  than  the  lower  portion  of  the  slope,  the  object  being 
that  a  steep  slope  from  i  on  i  to  i  £  reflects  the  waves,  while  a 
flatter  slope  breaks  them  up. 

The  top  width  of  the  dam  depends  somewhat  on  circum- 
stances. A  top  width  of  6  feet  is  perhaps  the  minimum  which 
should  be  employed,  and  for  a  high  dam  this  is  usually  too 
small.  A  good  rule  as  to  the  minimum  top  width  of  earthen 
dams  50  feet  in  height  and  over  is  to  make  their  breadth  10 
feet.  For  dams  under  50  feet  the  top  width  should  be  8  to  6 
feet.  As  the  dam  settles  in  course  of  time,  its  top  should  be 
built  up  by  adding  material  to  the  required  height.  The  dam 
should  always  be  several  feet  higher  than  the  highest  flood 
mark  in  order  to  prevent  waves  from  topping  it.  Thus  the 
height  of  the  dam  above  the  crest  of  the  discharge  weir  should 
be 


in  which  D  equals  the  depth  of  water  in  the  reservoir  above  the 

v/eir  crest  at  maximum  flood  ; 
^equals  the  height  of  the  top  of  the  stone   pitching 

above  the  surface  of  the  maximum  flood  ; 
C  is  a  constant  equal  to  2  or  3  feet  according  to  cir- 

cumstances, and  is  equal  to  the  vertical  height  of 

the  top  of  the  dam  above  the  top  of  the  pitching. 
227.  Foundations.—  The  foundation  of  an  earth  dam 
should  be  examined  with  great  care.  The  best  material  on 
which  to  found  it  is  sandy  or  gravelly  clay,  fine  sand  or  loam. 
Such  a  structure  should  never  be  built  on  shale  or  slate  or  on 
firm  rock.  Great  care  should  be  taken  in  searching  for  springs 
or  quicksands  in  the  foundation.  Sometimes  a  quicksand  may 
be  discovered  at  some  little  depth  beneath  a  hardpan  or  other 
suitable  foundation.  In  such  a  case  it  is  sometimes  possible  to 


226  EARTH  AND  LOOSE-ROCK  DAMS. 

seal  over  the  quicksand  under  the  embankment,  and  found  the 
latter  on  the  upper  stratum.  Such  an  expedient  is  not  entirely 
free  from  risk,  and  great  care  should  be  taken  in  joining  the  toe 
of  the  embankment  to  the  foundation  material,  if  necessary 
spreading  earth  and  clay  over  the  surface  of  the  valley  for  some 
distance  on  either  side  of  the  dam. 

The  first  thing  to  be  done  in  preparing  the  site  of  the  dam 
is  to  clean  off  all  soil,  removing  it  to  a  depth  equal  to  that 
penetrated  by  the  roots  of  the  grasses,  bushes,  and  trees.  If 
firm  and  impervious,  the  soil  may  be  scored  by  longitudinal 
trenches,  which  will  give  the  proper  adhesion  between  the 
foundation  and  the  embankment,  and  prevent  the  slipping  of 
the  latter.  If  a  puddle  wall  or  masonry  core  is  to  be  built 
into  the  dam,  the  foundation  for  this  should  be  sunk  to  a  suf- 
ficient depth  to  secure  its  permanence.  If  a  homogeneous  dam 
is  to  be  built  and  the  foundation  material  exposed  is  not  im- 
previous,  a  trench  should  be  dug,  and  this  filled  with  some 
puddle  material,  as  clayey  gravel  or  gravelly  loam,  moistened 
and  rolled  or  packed  in  layers. 

228.  Foundations  of  Masonry  Core  and  Puddle  Wall. 
— No  rule  can  be  laid  down  for  the  depth  to  which  the  founda- 
tions for  the  centre  wall,  if  one  is  built,  should  be  carried.  If 
a  rock  foundation  is  encountered  the  problem  is  simplified,  as 
the  wall  may  be  founded  on  this  after  removing  the  loose  and 
disintegrated  surface  ;  if  the  test  pits  or  borings  reveal  only  the 
existence  of  coarse  or  permeable  strata,  the  masonry  core  must 
be  carried  well  down.  In  some  cases  it  has  to  be  carried  to 
great  depths,  though  when  this  is  the  case  a  foundation  con- 
sisting of  a  puddle  wall  would  appear  to  be  preferable.  The 
finer  the  material,  the  better  it  is  adapted  for  a  foundation  for 
the  centre  wall.  Fine  gravel  and  sand  and  clay,  or  even  quick- 
sand when  at  a  sufficient  depth  to  prevent  its  being  forced  up, 
form  good  foundations. 

Where  a  puddle  wall  is  employed  instead  of  a  masonry 
core  or  heart-wall,  the  same  general  precautions  with  regard  to 
its  foundation  are  necessary  as  for  the  foundation  of  the  latter. 
Every  care  should  be  taken  to  insure  it  a  firm  seat  on  some 
impervious  stratum. 


SP  KINGS  IN  FOUNDATIONS— PUDDLE    W 'ALLS,  ETC.     227 

229.  Springs  in  Foundations. — It  is  a  very  common  oc- 
currence to  encounter  springs  in  the  excavations  for  the  foun- 
dations of  dams  either  of  masonry  or  of  earth.     These  springs 
are  a  great  menace  to  the  integrity  of  the  structure,  and  it  is 
due  to  their  presence  that  some  of  the  most  disastrous  failures 
of   dams   have   occurred.     Some    engineers   recommend   that 
springs  be  taken  up  and  carried  away  in  proper  drains  securely 
puddled.     This,  however,  is  a  very  difficult  operation  and  one 
rarely  possible  of  accomplishment.     When  a  single  large  spring 
is  discovered  this  mode  of  treatment  may  be  easily  resorted  to 
by  following  it  back  in  a  cutting  until  it  can  be  taken  up  in  a 
pipe.     But  ordinarily  the  foundation  is  underlain  by  a  number 
of  small  springs,  since  water  appears  in  such  cases  to  rise  from 
all   over   the  surface   of  the   stripped   foundation.     The   best 
method  of  dealing  with  such  cases  is  to  strip  the  foundation 
of  the  inner  embankment  down  to  good  firm  earth,  and  then 
commence  placing  that  part  of  the  embankment  which  is  next 
to  the  centre  wall  and  advance  it  outward  toward  the  toe  of  the 
slope  with   a  view   of  smothering   down   the  springs.     Large 
springs  frequently  give  trouble  in  closing  the  gap  in  the  foun- 
dation of  the  centre  wall.     They  may  sometimes  be  carried  up 
with  the  wall  until  a  point  is  reached  above  which  they  do  not 
rise,  or  they  may  be  handled  by  reducing  the  width  of  the  gap 
left  in  the  wall  until  it  becomes  too  narrow  for  the  passage  of 
the  water.     There  are  several  methods  of  treatment,  but  the 
rule  is  to  get  the  wall  built  up  so  that  the  water  does  not  wash 
out  the  mortar  and  run  through  it. 

230.  Masonry  Cores,  Puddle  Walls,  and  Homogeneous 
Embankments. — There  is  still  a  wide  difference  among  engi- 
neers as  to  the  best  type  of  earth  dam.     Occasionally  in  Eng- 
land and  in  a  few  cases  in  our  own  country  earth  dams  have 
been   built  up  homogeneously,  the  front   or  water  face  being 
covered  with  a  deep  layer  of  some  puddle  material,  as  clayey 
loam.     This  practice,  however,  is  falling  into  disuse,  and  engi- 
neers now  rarely  trust  to  a  puddle  face  alone   for  protection 
against  leakage. 

A  wooden  or  plank  core  should  never  be  employed.     The 


228  EARTH  AND  LOOSE-ROCK  DAMS. 

material  is  sure  to  rot  and  decay,  while  the  smooth  surface  of 
the  boards  offers  a  most  excellent  line  along  which  leakage 
water  will  travel  until  it  finds  an  outlet.  Again,  it  is  impossible 
to  make  a  wooden  wall  sufficiently  substantial  and  heavy  to 
withstand  leakage  and  the  tendency  to  rupture  which  may  re- 
sult from  the  settling  of  the  bank. 

The  masonry  core  is  in  great  favor  with  many  engineers, 
both  in  Europe,  India,  and  America.  A  central  core  of  puddled 
earth  is  subject  to  rupture  from  the  settlement  of  the  embank- 
ment. Both  are  practically  impervious  to  leakage.  In  build- 
ing them  they  must  be  carried  sufficiently  deep  to  reach  some 
impervious  stratum,  and  far  enough  into  the  side  walls  of  the 
valley  to  prevent  the  passage  around  their  ends  of  seepage 
water  which  would  travel  along  their  impervious  faces.  The 
construction  of  a  dam  composed  for  a  portion  of  its  length  of 
earth  and  for  the  remainder  of  loose  rock  or  masonry  is 
dangerous,  and  the  writer  is  opposed  to  such  combinations. 
Moreover,  masonry,  either  as  a  retaining  wall,  core,  or  culvert,  is 
rigid,  while  the  other  material  is  flexible,  and  any  settlement  in 
the  latter  leads  to  rupture  in  the  former.  Furthermore,  masonry 
offers  a  smooth  surface  for  the  travel  of  seepage  water. 

The  earth  dam  with  masonry  core  is  probably  the  most 
popular  at  present,  but  engineers  to  a  limited  extent  in  India 
and  to  a  large  extent  in  our  western  irrigation  region  are  com- 
ing to  favor  the  earth  dam  built  up  in  homogeneous  layers, 
each  carefully  rolled  or  tramped  over  in  such  a  manner  that  the 
whole  dam  is  a  puddle  wall.  This  character  of  construction 
has  all  the  advantages  of  imperviousness  to  leakage  if  the  work 
is  well  done,  while  it  is  free  from  the  disadvantages  possessed 
by  dams  with  central  cores,  namely,  a  smooth  surface  along 
which  water  may  travel,  and  liability  to  rupture  in  the  wall. 
To  be  sure,  the  liability  to  rupture  is  very  trifling,  and  is  a  mat- 
ter of  sentiment  and  theory  rather  than  fact,  as  probably  no  case 
is  on  record  of  such  an  accident  occurring  in  a  well-built  dam. 
Still,  a  homogeneous  earth  dam  (Art.  235)  is  one  of  the  sim- 
plest and  cheapest  to  construct,  and  may  be  so  built  up  as  to  be 
practically  indestructible.  With  such  a  form  of  dam  a  puddle 


MASONRY  COKES.         ,  229 

trench  is  usually  excavated  in  the  centre  of  the  foundation  and 
filled  with  puddle  material  to  prevent  leakage  under  and  around 
the  dam,  and  the  material  as  laid  down  may  be  so  selected  as 
to  get  the  finest  and  least  pervious  constituents  in  the  front 
portion  of  the  dam,  leaving  the  heavier  and  coarser  material  to 
the  rear  to  give  stability.  Such  a  form  of  construction  practi- 
cally converts  the  dam  into  one  having  a  puddle  face  of  great 
thickness. 

231.  Masonry  Cores. — The  primary  object  of  a  masonry 
centre  wall  is  to  afford  a  water-tight  cut-off  to  any  water  of  per- 
colation which  may  reach  it  through  the  bank.  Where  the 
masonry  wall  is  employed,  it  is  the  dam  proper,  for  it  is  this 
which  retains  the  water  in  the  reservoir,  the  earth  embankment 
surrounding  it  on  either  side  being  only  of  service  in  keeping 
the  centre  wall  from  being  thrown  down.  One  of  the  great  ad- 
vantages of  the  masonry  core  is  that  it  affords  an  excellent  op. 
portunity  for  making  the  connections  with  the  outlet  tower  and 
the  culverts  for  the  discharge  sluices.  These  masonry  culverts 
running  through  the  centre  of  an  earth  dam  constitute  one  of 
the  weakest  points  in  its  construction,  and  offer  the  greatest 
opportunity  for  the  passage  of  seepage  water.  They  can  be  so 
bonded  with  the  masonry  core  as  to  form  a  part  of  it,  and  pre- 
clude the  possibility  of  the  water  following  along  the  culverts. 

The  masonry  core  should  be  carried  to  a  height  equal  to 
that  of  the  sill  of  the  escape-way,  while  in  very  high  dams  it  is 
well  to  raise  it  to  the  extreme  flood  height.  It  should  be  as 
thin  as  possible  in  order  to  reduce  its  cost,  yet  as  some  move- 
ment may  take  place  in  the  embankment  owing  to  settlement, 
it  should  be  sufficiently  heavy  to  be  self-supporting.  A  safe 
and  usual  rule  is  to  give  it  a  top  width  of  4  to  5  feet,  and  to 
increase  its  thickness  toward  the  bottom  at  the  rate  of  about  I 
foot  in  10.  Sometimes  this  thickness  is  increased  beyond  the 
amount  here  stated.  This  centre  wall  should  be  composed  of 
the  best  hydraulic  masonry,  preferably  of  concrete  composed 
of  sharp  broken  stone  mixed  with  clean  sand  and  Portland 
cement.  Concrete,  however,  is  not  essential :  rubble  in  cement 
is  equally  good,  and  ordinarily  quite  as  convenient  and  satis- 


230  EARTH   AND  LOOSE-ROSK  DAMS. 

factory.  When  such  material  is  used,  however,  stones  of  mod- 
erate size  should  be  employed  which  shall  not  run  through  the 
wall  from  side  to  side,  and  for  purposes  of  economy  the  rubble 
should  be  uncoursed,  though  very  compactly  and  carefully  laid. 

An  excellent  example  of  a  masonry  core  or  centre  wall  for 
an  earth  dam  is  that  in  the  New  Croton  dam  at  Cornell's  (Fig. 
81).  This  masonry  core  is  18  feet  thick  at  the  base,  where  it 
is  founded  on  rock,  and  retains  the  same  dimensions  for  a  height 
of  89  feet,  above  which  it  tapers  to  6  feet  in  thickness  at  the 
top,  which  is  20  feet  below  the  top  of  the  embankment. 

232.  Puddle  Walls  and  Faces. — The  puddle  wall  is  not 
considered  as  satisfactory  nor  as  efficient  as  the  masonry  wall, 
though  it  is  much  cheaper  of  construction  in  some  portions  of 
the  West,  where  transportation  is  expensive.  The  proper  ma- 
terial for  a  puddle  is  not  always  obtainable,  while  water  for 
moistening  it  is  frequently  difficult  to  obtain  in  the  arid  region. 
It  is  difficult  to  prepare,  and  requires  careful  manipulation  in 
placing  it.  A  good  puddle  should,  when  placed,  resemble  in 
character  and  composition  an  unburnt  brick.  Where  too  much 
responsibility  is  rested  in  the  imperviousness  and  security  of 
the  puddle  wall  it  is  frequently  a  menace  to  the  structure,  as  it 
is  rarely  built  with  sufficient  care.  A  puddle  wall  should  have 
a  thickness  of  8  or  10  feet  at  the  level  of  the  water  line,  and 
should  increase  in  thickness  downward  to  the  surface  of  the 
ground  at  the  rate  of  about  I  foot  in  10.  Where  a  puddle  wall 
is  employed,  the  material  of  which  it  is  constructed  is  usually 
clay,  or  gravel  and  clay  moistened  and  puddled  in  layers  of 
about  6  inches  in  thickness,  and  permitted  to  dry  slowly. 
On  either  side  of  it  selected  material  is  usually  placed,  the 
remainder  of  the  dam  downward  consisting  of  the  poorer  and 
most  available  material. 

As  before  stated,  a  puddle  face  is  rarely  employed.  Where 
it  has  been  used  it  consists  generally  of  a  covering  on  the  whole 
inner  face  of  a  layer  of  puddle  8  or  10  feet  in  thickness  at  the 
base  and  2  or  3  feet  in  thickness  near  the  summit,  and  on 
the  whole  is  placed  a  layer  of  common  soil  on  which  the  rip- 
rap is  laid.  In  a  few  instances  the  puddle  face  has  been  mixed 


PUDDLE    TRENCH— EMBANKMENT.  231 

with  small  stones  or  furnace  cinders  as  an  obstruction  to  the 
passage  of  moles,  gopher,  or  other  vermin. 

233.  Puddle  Trench. — This  is  employed  only  where  the 
dam  is  built  up  in  homogeneous  layers  without  a  central  wall. 
1 1  consists  of  a  trench  excavated  longitudinally  the  entire  length 
of  the  dam  down  to  some  impervious  stratum,  or  if  none  can  be 
found,  for  a  very  considerable  depth.    This  trench  is  then  filled 
either  with  puddle  material  built  up  the  same  as  is  a  puddle 
wall  or  with  a  wall  of  masonry  built  up  as  a  core  wall,  and  the 
material  filling  this  trench  is  carried  up  several  feet  above  the 
surface  of  the  ground.     The  trench  should  be  carried  up  the 
slopes  of  the  surrounding  hills  till  it  terminates  at  a  level  with 
the  top  of  the  embankment,  and  its  bottom  should  be  level  in 
all  directions,  all  changes  of  level  being  made  by  means  of  ver- 
tical steps.     The  same  rule  applies  to  the  foundation  of  a  pud- 
dle wall  or  masonry  core. 

One  of  the  most  excellent  examples  of  a  puddle  trench  is 
that  illustrated  in  Plate  XX,  and  employed  in  the  Ashti  dam 
in  India.  This  trench  was  carried  down  to  a  hard  bed  of  trap- 
rock,  and  in  some  places  to  consolidated  clay.  In  this  a  puddle 
was  laid  in  layers  4  inches  thick  which  were  reduced  to  3 
inches  by  watering  and  rolling.  This  puddle  trench  is  rectan- 
gular in  cross-section,  10  feet  in  width  throughout,  and  gener- 
ally 1 6  feet  in  height  to  the  summit  of  the  material  filling  it. 
The  crest  of  the  material  filling  the  puddle  trench  was  raised 
to  a  height  of  I  foot  above  the  surface  of  the  ground  so  as  to 
form  a  water-tight  junction  with  the  earthwork  of  the  dam. 
Across  the  bed  of  the  river  along  the  centre  line  of  the  dam 
the  trench  was  made  but  5  feet  in  width,  and  was  carried  down 
to  bed-rock  and  extended  100  feet  into  the  banks  of  the  river 
on  either  side,  and  was  filled  with  a  wall  of  concrete. 

234.  Construction  of  Embankment. — As  ordinarily  built 
the    earth    embankment   changes   outward    from    the   central 
core,  as  before  described,  to  a  body  of  selected  material  on 
each  side  of  it,  the  remainder  of  the  dam  being  constructed  of 
the  most  available  common  material.     The  result  is  a  dam 
composed  of  5  layers,  each  of  different  density  and  weight  and 


HOMOGENEOUS  EARTH  EMBANKMENT.  233 

each  likely  to  settle  in  different  amount.  This  material  is  car- 
ried up  generally  in  layers  of  a  foot  or  so  in  thickness,  and  the 
result  is  a  structure  not  homogeneous  in  character  and  with  a 
series  of  horizontal  surfaces  with  cleavage  and  vertical  lines  on 
which  settlement  and  shrinkage  may  occur.  The  material, 
when  laid  in  the  embankment,  should  be  disposed  in  layers 
which  are  thicker  at  their  outer  edges  than  at  the  centre. 

When  well  built  the  centre  third  of  the  dam  is  composed  of 
the  best  selected  material,  while  on  either  side  of  it  is  laid  com- 
mon soil,  which  is  usually  not  so  impervious  to  water  as  that  in 
the  centre.  On  the  lower  side  of  the  dam  is  laid  any  heavy 
material  available.  The  main  object  in  constructing  an  earth 
dam  which  has  some  impervious  central  core  is  to  make  this 
central  wall  and  a  small  portion  of  the  bank  in  the  rear  and  a 
large  section  in  front  impermeable  to  the  percolation  of  water ; 
then  the  remainder  of  the  bank  to  the  rear  is  put  in  merely 
with  the  object  of  giving  stability  to  the  water-tight  portion. 

235.  Homogeneous  Earth  Embankment.— This  type  of 
dam  is  considered  by  the  writer  and  many  other  engineers  as 
the  most  safe  and  efficient  as  well  as  economic.  It  is  gen- 
erally preferable  in  the  arid  region  because  of  the  saving  in 
transportation  of  cement,  rock,  or  selected  materials  for  a  pud- 
dle wall.  Such  a  dam  .should  be  of  the  same  density  through- 
out, and  composed  of  material  practically  impervious  to  water. 
It  should  form  in  itself  and  with  the  natural  material  on  which 
it  rests  a  perfectly  homogeneous  mass.  Practically  it  is  diffi- 
cult to  obtain  such  a  structure,  though  the  engineer  should  come 
as  near  as  possible  to  the  ideal.  A  puddle  or  masonry  core  is 
considered  by  some  Western  engineers  as  an  element  of  weak- 
ness in  the  structure.  They  say  that  in  a  homogeneous  earth 
dam  the  up-stream  face  is  that  point  at  which  the  water  press- 
ure ceases  either  by  the  water  ceasing  to  penetrate  the  body 
of  the  dam  or  by  its  having  free  egress  from  the  down-stream 
side.  The  puddle  or  masonry  wall  will  stop  the  small  amount 
of  water  coming  through  a  new  dam,  and  this  will  accumulate 
in  the  earth  against  the  core,  and  will  finally  permeate  the 
whole  body  of  the  dam  above  the  wall,  thus  causing  the  water 


234  EARTH  AND    IOOSE-ROCK  DAMS. 

pressure  which  should  be  exerted  against  the  up-stream  face 
to  be  exerted  against  the  core.  The  whole  duty  of  the  dam  is 
then  performed  by  the  masonry  core  and  the  material  below 
it. 

If  enough  impervious  material  cannot  be  had  to  build  the 
whole  structure  up  homogeneously  in  layers,  the  up-stream  third 
or  half  should  be  built  of  the  best  material  available,  the  poor- 
est and  heaviest  being  put  in  the  lower  side.  These  two  classes 
of  material  should  be  well  worked  into  one  another  so  as  to 
give  a  perfect  bonding.  This  practically  converts  the  principal 
third  of  the  dam  into  a  puddle  face,  only  the  whole  structure 
is  built  up  at  the  same  time  in  irregular  layers  of  I  or  2  feet  in 
thickness,  and  well  tramped  over  or  puddled.  By  not  building 
it  in  uniform  layers  a  better  bond  is  given  to  the  structure. 
With  such  a  form  of  construction  any  water  which  may  soak 
through  the  upper  third  will  find  free  egress  from  the  dam  on 
its  lower  side.  The  result  will  be  to  keep  water  out  of  the  dam 
if  possible,  but  when  it  enters  to  pass  it  through  quickly.  In 
building  a  dam  up  in  irregular  layers  in  this  way  these  layers 
should  be  so  disposed  that  the  outer  edges  or  extremities  of 
each  layer  shall  be  higher  than  the  centre  of  the  layer  by  from 
2  to  4  feet.  As  built  in  the  West  with  teams  and  scrapers,  no 
runways  should  be  provided,  the  teams  being  driven  over  the 
whole  surface,  thus  adding  to  the  density  and  compactness  of 
the  structure.  As  each  layer  is  built  up  it  is  well  to  drag  or 
harrow  it,  and  then  pass  a  heavy  roller  over  it.  The  same  re- 
sult can  be  produced  by  rolling  it  with  a  heavy  roller  having 
annular  projections  or  rings  on  its  surface. 

236.  Embankment  Material. — The  ideal  material  of  which 
to  construct  an  earth  dam  is  such  a  mixture  of  gravel,  sand, 
and  clay  that  all  the  coarser  interstices  between  the  particles 
of  the  former  shall  be  filled  by  the  sand,  and  that  all  the  mi- 
nute openings  between  the  particles  of  this  material  shall  be 
filled  by  the  still  finer  particles  of  clay.  This  would  give  such 
a  composition  that  water  would  pass  through  it  with  the  great- 
est amount  of  resistance,  and  the  bank  would  be  practically 
impervious.  In  practice,  with  proper  care  to  mix  the  materials 


EMBANKMENT  MATERIAL— INTERIOR   SLOPE.          235 

so  as  to  thoroughly  incorporate  them  one  with  the  other,  the 
following  proportions  should  be  used  : 

Coarse  gravel i.oo  cubic  yard 

Fine  gravel 0.35  " 

Sand 0.15 

Clay 0.20  " 

Giving  a  total  of  about  1.70  cubic  yards,  which  when  well  mixed, 
compacted,  and  rolled  can  be  reduced  to  about  \\  cubic 
yards  in  bulk.  These  proportions  will  rarely  be  obtained,  but 
the  effort  should  be  to  approach  as  nearly  to  them  as  possible 
in  order  to  produce  the  best  combination  of  materials.  Weight 
is  a  valuable  property  in  an  earth  embankment,  and  such  a 
combination  as  above  given  possesses  the  greatest  amount  of 
weight  obtainable  with  earth.  The  sand  and  gravel  lack 
cohesiveness  but  have  stability,  while  clay  though  cohesive  is 
liable  to  slip  if  unsupported.  The  combination  above  given 
possesses  the  qualities  of  weight,  cohesiveness,  stability,  and 
imperviousness,  while  the  angle  of  repose  or  the  slope  which 
can  be  given  is  about  midway  between  that  possible  with  fine 
sand  and  that  to  be  obtained  with  shingle  or  a  mixture  of  sand 
and  clay.  If  judgment  be  used  in  choosing  materials,  dirty 
gravel,  or  that  possessing  a  large  amount  of  soil  and  sandy 
matter,  may  often  be  found  which  will  give  nearly  the  propor- 
tions above  specified. 

237.  Interior  Slope  and  Paving. — The  interior  slope  of  an 
earth  dam  is  rarely  made  uniform,  while  the  exterior  slope 
though  usually  uniform  is  sometimes  broken  by  a  level  bench 
(Fig.  81),  the  object  of  which  is  to  prevent  serious  effect 
from  the  sliding  of  the  embankment.  This  bench  is  usually 
made  from  4  to  6  feet  in  width.  On  the  interior  slope  one  or 
more  similar  benches  are  sometimes  introduced,  though  rarely 
more  than  one.  In  the  case,  however,  of  the  great  dam  being 
built  for  the  Citizens'  Water  Company  in  Denver  the  slope  is 
to  be  broken  by  a  number  of  benches.  In  addition  to  this  break 
in  the  slope,  it  is  not  uncommon  to  give  a  lighter  slope  below 


236  EARTH  AND    LOOSE-ROCK  DAMS. 

the  bench  and  a  steeper  inclination  for  the  last  5  to  7  feet  at  the 
top  of  the  inner  slope  (PL  XX).  This  steepness  at  the  top  is 
to  prevent  waves  at  flood  height  from  slopping  over  the  crest 
of  the  embankment,  the  sharp  angle  breaking  the  waves  up  and 
reflecting  them  back.  The  bottom  of  the  inner  slope  is  some- 
times made  steeper  if  the  material  will  stand  it,  as  it  is  not 
exposed  to  the  air  by  the  drawing  off  of  the  water  as  is  the 
upper  portion  of  the  embankment. 

This  interior  slope  is  invariably  paved  with  cobble-stones  or 
dry  rubble  tightly  driven  home  and  carefully  placed  (PL  XX). 
The  object  of  this  pitching  is  to  protect  the  embankment 
against  the  erosive  action  of  the  waves,  and  its  thickness  de- 
pends on  the  height  and  violence  of  these.  The  maximum 
height  of  the  waves  depends  on  the  fetch  or  distance  from  the 
shore  where  their  formation  commences,  and  may  be  determined 
by  Stephenson's  formula, 

X=  i.  5  ^+2.5 


where  X  equals  the  height  of  wave  in  feet  and  F  equals  the 
fetch  in  nautical  miles.  Rankine  states  that  where  an  embank- 
ment of  loose  stone  is  exposed  to  the  action  of  the  waves  it 
should  be  faced  with  blocks  set  by  hand,  the  least  dimension 
of  any  block  in  the  facing  being  not  less  than  two  thirds  the 
greatest  wave  height.  The  best  way  in  which  to  lay  the 
stones  is  to  place  them  with  broad  ends  downwards,  rough 
squared  stones  being  preferable,  in  order  that  they  shall  fit 
fairly  close  one  to  the  other.  The  interstices  should  be  packed 
with  small  stone  chippings  and  finished  off  with  earth  (Fig.  81). 
The  entire  height  of  the  inner  slope  need  not  be  protected 
by  a  stone  pitching.  That  portion  of  the  slope  which  is  below 
the  level  of  the  outlet  sluices  requires  no  pitching  at  all,  as  it 
will  not  be  subjected  to  wave  action.  The  lower  portion  of 
the  exposed  slope  need  be  pitched  with  a  lesser  thickness  than 
the  upper  portion,  as  the  fetch  will  be  less,  and  consequently 
the  wave  height  less  and  its  erosive  action  proportionately 
diminished.  At  the  upper  portion  of  the  slope  the  pitching 
should  be  carried  quite  to  the  top  of  the  embankment,  and  for 


EMBANKMENT    WITH  MASONRY  RETAINING    WALL. 

safety  might  be  carried  across  the  top,  in  order  that  any  spray 
falling  on  the  top  of  the  embankment  should  do  the  least  pos- 
sible amount  of  damage.  It  is  customary  to  give  the  top  of 
the  embankment  a  slight  inclination  toward  the  reservoir,  so 
that  it  will  drain  into  it  and  not  outward  over  the  unprotected 
lower  slope.  For  better  protection  of  this  exterior  slope  it 
should  be  planted  with  grass,  or,  better  still,  sods  of  consider- 
able size  should  be  placed  upon  it  a  few  feet  apart,  in  order 
that  the  roots  of  these  may  spread  and  entirely  protect  it  from 
the  erosive  action  of  rain  and  spray. 

238.  Earth  Embankment  with  Masonry  Retaining 
Wall. —  It  is  sometimes  necessary  to  economize  reservoir 
space,  in  which  case  one  side  of  the  embankment  may  be 


A 


FIG.  64.— CROSS-SECTIONS  OF  KABKA  DAM  (A)  AND  EKRUK  DAM  (.5),  INDIA. 

faced  with  masonry,  though  this  combination  is  rarely  success- 
ful or  advisable.  It  has  all  the  disadvantages  of  both  earth 
and  masonry  dams  without  any  additional  advantages.  The 
Kabra  embankment  in  India  (Fig.  64,  A)  is  an  example  of  this 
class  of  structure.  It  consists  of  a  masonry  wall  on  the  front 
face  of  an  earth  embankment  and  having  a  steep  batter  of 
about  12  on  I,  while  the  outer  portion  of  the  embankment 
and  the  lower  slope  have  the  natural  slope  of  the  earth,, 
which  is  merely  used  to  give  stability  to  the  masonry  facing 
wall,  the  latter  being  the  dam  proper. 


1 


PECOS  DAM,  239 

The  masonry  may  be  put  in  as  in  the  case  of  the  Ekruk 
tank  in  India  (Fig.  64,  B).  This  consists  of  a  masonry  core  of 
such  dimensions  as  to  practically  form  the  entire  dam,  the  earth 
being  merely  added  to  the  bottom  of  the  slopes  to  give  stabil- 
ity. In  this  case  the  masonry  dam  has  an  inner  slope  of  12  on 
I,  an  outer  slope  of  2  on  I,  and  a  total  height  of  68  feet.  Against 
it,  on  its  upper  side,  is  an  earth  embankment  with  a  slope  of  I 
on  3,  reaching  to  about  25  feet  in  height,  and  on  the  outer  slope 
another  earth  embankment  with  a  slope  of  I  on  2,  reaching  to 
about  35  feet  in  height.  Above  this  the  masonry  is  unsupported. 
Still  another  method  of  using  masonry  with  earth  is  where  the 
inner  slope  of  the  dam  is  of  earth,  its  water  face  being  rip- 
rapped  as  before  described  and  a  puddle  wall  placed  through 
its  centre  to  prevent  percolation.  On  the  outer  slope,  in  place 
of  the  usual  mass  of  material  intended  to  add  stability,  is  built 
up  a  rubble  retaining  wall,  the  stones  being  set  in  mortar,  the 
object  of  the  wall  being  merely  to  retain  the  embankment,  and 
not  to  prevent  percolation  ;  also  to  avoid  covering  land  below 
the  dam  which  may  be  of  value. 

239.  Earth  and  Loose-rock  Dams. — Pecos  Dam. — The 
dam  at  the  head  of  the  Pecos  Irrigation  Company's  canal,  in 
New  Mexico  (PL  XXI),  furnishes  an  excellent  example  of  this 
combined  construction.  This  dam  is  shaped  in  plan  like  the 
letter  L,  the  re-entrant  angle  of  which  points  up-stream.  The 


<5<J 


FIG.  65.— CROSS-SECTION  OF  PECOS  DAM. 


long  arm  which  composes  the  main  dam  is  1070  feet  in  length 
and  varies  from  5  to  50  feet  in  height ;  the  short  arm  consists 
of  a  simple  earth  embankment  530  feet  in  length,  with  an 
average  height  of  52  feet.  Adjacent  to  the  end  of  the  dam 


240  EARTH  AND  LOOSE-ROCK  DAMS. 

farthest  from  the  headgate  is  a  wasteway  250  feet  wide,  exca- 
vated in  limestone  rock,  its  bed  being  5  feet  below  the  crest  of 
the  dam.  This  wasteway  is  300  feet  long  and  has  a  grade  of 
I  in  3.  At  the  lower  end  of  the  rock  cut  on  the  left  bank  of 
the  river  is  an  additional  wasteway  just  below  the  end  of  the 
dam.  This  wasteway  has  a  total  length  of  206  feet,  its  sill  being 
about  2  feet  lower  than  the  one  first  mentioned.  The  main  dam 
(Fig.  65)  is  composed  of  a  prism  of  loose  rock  12  feet  wide  on 
top,  100  feet  wide  at  bottom,  with  a  lower  or  outer  slope  of  i  on 
i  J-  and  an  inner  slope  of  I  on  £.  Its  maximum  height  is  50  feet, 
and  the  up-stream  face  is  backed  with  an  earth  embankment  the 
width  of  which  is  10  feet  at  top  and  200  feet  at  the  bottom  ; 
its  up-stream  slope  being  I  on  3^  and  paved  with  18  inches  of 
stone  riprapping.  The  lower  portion  of  this  slope  near  the  out- 
let sluice  is  replaced  by  10  feet  in  depth  of  loose  rock  for  a  total 
width  through  the  dam  of  75  feet,  to  prevent  undercutting  by 
currents.  At  the  top  of  the  outer  slope  is  a  low  masonry  wall 
5  feet  in  height  and  2  feet  in  width,  built  as  a  retaining  wall  to 
give  the  requisite  top  width  to  the  embankment.  In  the  bottom 
of  the  dam  near  the  end  adjacent  to  the  canal  head  is  an  under- 
sluice  the  sill  of  which  is  37  feet  below  the  dam  crest.  This 
sluice  is  4  by  8  feet  in  the  clear  and  has  a  grade  of  1.2  in  100, 
its  discharge  capacity  with  a  full  reservoir  being  2000  second- 
feet.  The  lining  ctf  the  culvert  composing  the  undersluice  is 
of  rubble  masonry  8  feet  in  thickness. 

240.  Loose  Rock  and  Earth  Dam. — Idaho  Dam. — An 
excellent  example  of  this  class  of  structure  is  that  being  built  at 
the  head  of  the  Idaho  Mining  and  Irrigation  Company's  canal 
(Fig.  66).  The  site  of  this  dam  is  at  a  point  where  solid  basalt  out- 
crops across  the  channel  of  the  Boise  river,  and  the  dam  is  to  be 
founded  on  this.  Just  above  the  dam  is  a  basalt  ledge  12  feet  in 
height  which  borders  the  river  bank,  and  on  this  will  be  con- 
structed the  wasteway,  with  a  width  of  450  feet.  This  wasteway 
is  to  be  excavated  in  gravel  and  carried  to  a  depth  of  8  feet  below 
the  crest  of  the  dam.  It  will  be  720  feet  in  length,  and  will  dis- 
charge back  into  the  river  100  feet  below  the  dam.  In  it  will  be 
built  a  waste  weir  of  rubble  masonry  across  the  entire  width  of  the 


IDAHO   DAM. 


241 


channel  and  founded  on  the  basalt  underlying  the  gravel.  The 
object  of  this  weir  is  to  make  the  crest  of  the  wasteway  at  the 
required  height  with  relation  to  that  of  the  main  dam.  Its  pro- 


FIG.  66. — PLAN  OF  IDAHO  DAM. 

posed  cross-section  is  peculiar,  its  base  being  19  feet  in  width  and 
its  maximum  height  8  feet.  Its  upper  slope  will  have  a  batter 
of  6  on  i,  while  its  lower  slope  will  have  an  ogee-shaped  curve. 
The  main  dam  (Fig.  67)  is  to  be  constructed  of  loose  rock 
with  an  earth  facing.  It  will  be  220  feet  in  length  on  its  crest  and 


FIG.  67.— CROSS-SECTION  OF  IDAHO  DAM. 

43  feet  in  maximum  height,  its  top  width  being  10  feet,  of  which 
3  feet  on  the  inner  slope  will  consist  of  the  top  of  the  earth 
backing,  which  at  the  bottom  of  the  dam  is  to  be  20  feet  in  width. 
The  lower  or  rock  face  of  the  dam  will  have  a  slope  of  if  on  I, 
the  up-stream  or  earth  slope  of  the  rockwork  being  the  same. 


242  EARTH  AND   LOOSE-ROCK  DAMS. 

241.  Loose-rock  Dams. — When  properly  constructed  and 
well  founded  there  is  no  apparent  reason  why  a  loose-rock  dam 
should  not  be  nearly  as  substantial  as  one  of  masonry.  Such 
dams  should  be  founded  only  on  solid  rock,  hardpan,  or  on 
beds  of  very  stiff  clay  or  other  unwashable  material.  This  dam 
is  the  outcome  of  Western  engineering  practice,  and  was  first 
introduced  for  the  purpose  of  storing  water  for  placer  mining: 
hence  it  is  generally  known  as  the  hydraulic-mining  type  of  dam. 
It  consists  of  a  mass  of  loose  rock  placed  together  with  some 
degree  of  care,  the  smaller  stones  being  used  to  fill  the  inter- 
stices between  the  larger  ones  so  that  the  settlement  shall  be 
the  least  possible.  Such  slopes  are  given  the  mass  as  it  can 
safely  stand,  and  it  is  rendered  impervious  to  water  by  a  heavy 
sheathing  of  tarred  planking  or  an  earth 'embankment  on  its 
upper  face.  Water  should  not  be  permitted  to  flow  over  the 
crest  or  back  of  such  a  structure,  as  it  is  liable  to  cause  settle- 
ment which  may  result  in  its  rupture. 

It  is  claimed  by  their  advocates  that  rock-filled  dams  are 
cheaper  than  those  of  masonry  or  earth.  The  latter  is  unques- 
tionably cheaper  than  a  rock-filled  dam  in  nearly  every  case, 
while  if  transportation  is  not  expensive  a  masonry  dam  is  fre- 
quently cheaper  than  a  rock-filled  dam  owing  to  the  difference 
in  cross-section  and  the  correspondingly  small  amount  of 
material  required  in  the  former,  though  the  cost  per  cubic 
yard  is  relatively  high.  One  of  the  great  advantages  of  the 
rock-filled  dam  is  that  it  may  be  constructed  with  very  little 
difficulty  in  flowing  water;  another  advantage  is  that  a  leak  is 
not  the  menace  it  is  in  an  earth  or  masonry  dam,  since  the 
whole  structure  is  expected  to  leak.  A  masonry  dam  is,  during 
its  existence,  in  a  state  of  unstable  equilibrium,  while  a  rock- 
filled  dam  from  the  process  of  its  construction  tends  to  improve 
with  time,  and  if  properly  built  it  may  be  benefited  by  causes 
which  threaten  other  dams.  Such  a  dam  as  this  should  not  be 
used  where  water  is  valuable  unless  great  care  is  taken  in  pro- 
viding against  leakage,  and  this  can  only  be  well  done  when  an 
earth  filling  or  facing  is  used.  In  preparing  the  foundation 
for  a  loose-rock  dam  the  only  precaution  necessary  is  that  it 


WALNUT  GROVE  DAM.  243 

shall  be  founded  on  impervious  and  unwashable  material. 
If  there  be  a  surface  covering  of  loose  soil  or  gravel  it 
should  either  be  removed  by  carts,  or  if  the  current  in  the 
stream  is  sufficient  it  may  be  washed  away  as  the  dam  is 
built  up. 

A  loose-rock  dam  should  be  built  up  in  layers  as  is  done 
with  an  earth  dam,  and  in  such  manner  that  the  centre  of  each 
layer  shall  be  lower  than  the  outer  extremities.  The  best 
cross-section  for  such  a  dam  is  an  upper  slope  of  ^  to  £  on  I 
and  a  lower  slope  of  I  on  I  ;  anything  less  than  this  cannot  be 
considered  secure. 

242.  Walnut  Grove  Dam. — This  is  an  excellent  example 
of  the  rock-filled  dam.  It  was  destroyed  in  February,  1890, 
by  a  great  flood,  though  its  destruction  was  not  a  result  of 
faulty  design,  but  of  carelessness  in  one  or  two  details  of  its 
construction, — notably  in  the  failure  to  provide  an  ample  waste- 
way  and  in  the  careless  manner  in  which  the  stones  were 
dumped  in  the  centre  of  the  structure.  This  dam  (Fig.  68) 
rested  on  the  firm  rock  of  the  stream  bed  throughout  its  length, 
with  the  exception  of  a  small  portion  of  the  upper  wall,  which 
is  believed  to  have  rested  on  from  5  to  12  feet  in  depth  of 
loose  earth  and  gravel.  This  was  one  of  the  weak  points  of 
its  construction. 

The  dam  was  420  feet  long  on  top,  138  feet  wide  at  the 
bottom,  15  feet  in  width  on  top,  and  no  feet  in  greatest 
height,  and  contained  nearly  50,000  cubic  feet  of  material.  It 
consisted  of  a  front  and  back  wall,  each  14  feet  thick  at  the 
base  and  4  feet  on  top,  with  a  loose-rock  filling  between ;  the 
whole  made  water-tight  by  a  wooden  sheathing.  The  upper 
slope  of  the  dam  was  2\  on  I  and  the  lower  slope  ij  on  I. 
This  latter,  however,  was  increased  for  the  lower  half  of  the 
dam  to  about  I  on  I  by  the  addition  of  a  pile  of  loose  rock 
after  the  completion  of  the  structure.  The  wooden  sheathing 
consisted  of  logs  from  8  to  10  inches  in  diameter  and  from  6  to 
12  feet  in  length,  built  into  the  wall  on  its  upper  face  and  pro- 
jecting therefrom  about  I  foot.  The  upper  and  lower  faces 
consisted  of  rough  blocks  of  granite  dry-laid  in  such  manner  as 


244 


EARTH  AND  LOOSE-ROCK  DAMS. 


to  form  two  loose-rock  retaining  walls,  between  which  the  body 
of  the  loose  stone  was  dumped.  Vertical  stringers  about  8  by 
IO  inches  were  bolted  to  the  projecting  ends  of  the  logs  built 
into  the  upper  face,  and  these  stringers  were  placed  about  4 


400FI 


FIG.  68. — ELEVATION  AND  CROSS-SECTION  OF  WALNUT  GROVE  DAM. 

feet  apart.  Upon  the  face  of  the  dam  and  over  these  string- 
ers two  thicknesses  of  3  by  8  inch  planking  were  spiked,  and 
tarred  paper  was  laid  between  the  two.  The  outer  face  of  this 
sheathing  was  finally  calked,  and  the  whole  covered  with 
paraffine  paint. 

243.  Crib  Dams. — The  general  form  of  construction  and 
several  examples  of  crib  weirs  were  given  in  Articles  132,  133. 


CRIB   DAMS. 


245 


Structures  of  similar  design  have  occasionally  been  built  of 
sufficient  height  to  form  storage  reservoirs.     The  employment 


PLAN 


FIG.  69. — PLAN  AND  CROSS-SECTION  OF  BOWMAN  DAM. 

of  cribwork  in  a  storage  dam  is  not  recommended,  as  such 
work  is  essentially  temporary  in  character.  As  a  result  of  the 
alternate  wetting  and  drying  which  it  receives  it  is  very  liable 
to  rot,  and  the  life  of  such  a  dam  is  manifestly  shorter  than 
that  of  an  earth,  loose-rock,  or  masonry  dam. 


246  EARTH  AND  LOOSE- ROCK  DAMS. 

Several  types  of  crib  and  combined  crib  and  loose-rock 
dams  have  been  constructed  in  the  Sierras  of  California  for 
the  storage  of  water  for  hydraulic  mining.  One  of  the  most 
notable  of  these  was  the  crib  and  loose-rock  dam  built  to  close 
the  English  reservoir  in  Sierra  county,  California.  This  con- 
sisted of  the  usual  form  of  timber  crib  made  of  tamarack  logs 
and  filled  with  stones.  The  height  of  this  dam  was  79  feet, 
and  its  width  at  the  base  100  feet,  the  inner  slope  being  a  trifle 
steeper  than  i£  on  I  and  the  outer  slope  i^  on  I.  The  water 
face  was  covered  with  a  heavy  planking  of  pine,  thus  forming  a 
water-tight  lining  to  the  dam.  The  lower  slope  of  this  crib- 
work  was  backed  up  by  a  loose-rock  filling,  hand-placed  on  the 
surface  so  as  to  have  an  even  slope ;  the  width  of  this  filling 
being  55  feet  at  the  base  and  8  feet  on  top,  its  outer  slope 
being  I  on  I.  The  discharge  sluice  of  this  dam  consisted  of  a 
timber  culvert  built  through  it  at  its  base. 

Another  typical  dam  of  the  same  type  is  the  Bowman  dam, 
used  for  water  storage  by  the  North  Bloomfield  Mining  Com- 
pany, in  California.  This  dam  (Fig.  69)  has  a  total  height  of 
100  feet  and  uniform  slopes  on  both  faces  of  I  on  I.  Its  lower 
third  on  the  up-stream  side  consists  of  a  cribwork  of  logs  filled 
with  rock,  the  cross-section  of  which  is  I  on  I,  while  the  re- 
mainder of  the  dam  consists  of  loose  rock  hand-placed  and 
carefully  laid.  The  upper  slope  of  the  dam  is  sheathed  with 
planking  and  the  lower  slope  is  faced  with  rubble  masonry  laid 
in  cement.  Through  the  bottom  of  the  dam  is  an  outlet  cul- 
vert constructed  of  masonry  and  cement. 

244.  Loose-rock  Dam  with  Masonry  Retaining  Walls. 
— Probably  the  only  existing  example  of  this  type  of  construc- 
tion is  that  closing  the  Castlewood  reservoir  in  Colorado.  This 
dam  (Fig.  70)  is  founded  on  a  bed  of  clay  and  bowlders  from  7 
to  30  feet  in  depth,  and  is  composed  of  an  outer  shell  or  wall 
of  large  blocks  of  coarse  rubble  masonry,  the  thickness  of 
which  on  the  up-stream  face  is  about  6  feet  on  top  and  12  feet 
at  the  bottom.  On  the  down-stream  face  the  wall  is  from  5 
to  7  feet  in  thickness,  this  face  being  laid  in  steps  the  height  of 
which  vary  from  \\  to  2\  feet  according  to  the  dimensions  of 


CASTLEWOOD   DAM. 


247 


the  stone  blocks  forming  them.  The  main  body  or  centre  of 
the  dam  consists  of  dry-laid  rubble  enclosed  between  these 
two  walls.  The  maximum  height  of  the  dam  is  63^  feet,  it  is 
586  feet  in  length  on  the  crest,  and  100  feet  of  this  length  is 
lowered  4  feet  in  order  to  form  a  wasteway  over  which  flood 
waters  may  discharge.  The  upper  4  feet  of  this  dam  is  vertical 
on  both  sides,  and  its  top  is  8  feet  in  width  and  constructed 
of  rubble  masonry  in  cement.  The  outer  slope  of  the  remain- 
der of  the  dam  is  i  on  i,  while  the  inner  slope  is  10  on  i.  It 


set' 
Plan 
<     iso'  > 


FIG.  70. — ELEVATION,  PLAN.  AND  CROSS-SECTION  OF  CASTLEWOOD  DAM. 

is  possible  that  in  the  future  such  a  type  of  dam  as  this  may 
become  popular.  It  possesses  all  the  good  qualities  of  the 
loose-rock  dam  and  need  be  no  more  expensive,  since  its 
slopes  may  be  made  a  little  steeper.  It  is  doubtful  if  so 
steep  a  slope  as  10  on  i  for  the  upper  face  is  safe  :  probably  5 
on  i  would  be  better,  while  i  on  i  for  the  rear  face  is  ample 
to  give  stability.  In  such  a  structure  as  this  great  care 
should  be  taken  to  firmly  found  it  on  solid  rock  or  on  a  deep 
bed  of  hard  and  impervious  clay,  while  the  loose-rock  centre 
should  be  carefully  laid  to  prevent  any  inclination  to  slide  or 
thr.K'-  outward  against  the  confining  walls. 


CHAPTER   XIX. 
MASONRY    DAMS. 

245.  Theory  of  Masonry  Dams. — Masonry  dams  are 
employed  both  for  diversion  and  storage  works,  and  may  be  so 
constructed  as  either  to  permit  flood  water  to  pass  over  their 
crests  or  have  it  passed  around  one  end.  If  the  dam  is  to  be 
used  for  storage  purposes  only,  and  a  sufficient  wasteway  can 
be  provided,  it  may  be  designed  according  to  one  of  the  theo- 
retical formulas  or  from  one  of  the  type  profiles  given  here- 
after. Dams  constructed  by  these  formulas  contain  the  mini- 
mum amount  of  material  necessary  to  enable  them  to  perform 
their  functions  of  holding  up  the  storage  water,  and  are  not 
sufficiently  substantial  to  withstand  the  shock  produced  by 
water  falling  over  their  crests.  Where  a  masonry  dam  is  used 
as  a  diversion  weir  or  as  an  overflow  weir,  it  is  impossible  to 
design  it  on  any  of  the  theoretical  profiles.  The  chief  calcula- 
tion then  requisite  in  its  design  is,  that  the  pressure  of  the 
masonry  on  the  foundation  shall  not  pass  the  limit  which  the 
material  can  withstand,  and  also  that  its  cross-section  shall  be 
more  ample  and  substantial  than  that  which  would  be  required 
by  one  of  the  theoretical  profiles. 

The  first  and  most  vital  rule  in  building  a  masonry  dam  is 
that  it  shall  rest  on  solid  and  practically  homogeneous  rock. 
A  masonry  dam  is  practically  an  absolutely  rigid  structure, 
and  settlement  in  any  portion  of  its  foundation  will  result  in 
cracks  and  ultimate  rupture  in  its  mass.  There  are  two  ways 
in  which  a  masonry  dam  may  resist  the  thrust  of  water :  first, 

248 


THEORY  OF  MASONRY  DAMS. 


249 


by  the  inertia  or  weight  of  its  mass,  and,  second,  as  an  arch. 
Its  safety  depends  upon  compliance  with  the  conditions — 

1.  That  the  horizontal  thrust  of  the  water  must  be  held  in 
equilibrium  by  the  resistance  of  the  masonry  to  sliding  forward 
or  overturning  ;  and, 

2.  That  the  pressure  sustained  by  the  masonry  or  its  foun- 
dation must  never  exceed  a  certain  safe  limit. 

The  thrust  of  the  water  may  be  resisted  by  being  transmit- 
ted to  the  abutments,  the  dam  acting  as  an  arch.  But  three 
dams  have  as  yet  been  built  which  depend  in  any  degree  for 
their  stability  on  arch  action,  and  the  laws  governing  this 
action  in  a  dam  are  as  yet  so  uncertain  that  they  cannot  be 
depended  upon  with  any  degree  of  security.  Some  attempt 
at  solving  the  rules  on  which  a  dam  is  dependent  for  its  stabil- 
ity as  an  arch  are  given  in  Articles  255  and  256.  According  to 
J.  B.  Krantz,  a  dam  which  is  curved  in  plan,  with  a  radius  of 
65  feet  or  less  will  transfer  the  pressure  of  the  water  to  the 
sides  of  the  valley  whatever  the  height  of  the  structure.  This, 
however,  does  not  lessen  the  effect  of  the  weight  of  the 
masonry,  so  that  whether  the  structure  be  curved  in  plan  or 
not,  its  weight  must  be  supported  in  the  same  way,  and  the 
height  must  be  such  that  this  weight  will  not  exceed  the  limit 
of  pressure  permissible  on  the  base.  In  France,  and  in  the  case 
of  the  Fife  dam  near  Poona,  India,  and  elsewhere,  reservoir 
walls  have  been  reinforced  by  means  of  masonry  counterforts. 
If  the  wall  is  strong  enough  by  itself  the  counterforts  are  a 
useless  expense,  and  if  the  wall  is  not  sufficiently  strong  they 
will  not  prevent  it  from  yielding.  The  masonry  intended  for 
the  counterforts  would  always  be  better  used  if  spread  over  the 
mass  of  the  dam. 

246.  Stability  of  Gravity  Dams.— The  author  will  make 
no  attempt  here  to  enter  into  a  tedious  mathematical  discussion 
of  the  theory  of  the  stability  of  masonry  dams.  This  question 
is  one  which  has  been  investigated  with  great  thoroughness 
within  the  past  15  years,  and  nothing  which  could  be  stated  in 
this  place  will  add  to  the  value  of  the  theories  now  held.  For 
the  benefit  of  students  who  desire  to  enter  into  the  mathematics 


250  MASONRY  DAMS. 

of  this  subject  a  list  of  authors  is  appended  at  the  end  of  this 
chapter.  Sufficient  of  the  principles  of  the  subject  may  be 
obtained  from  the  works  of  Baker,  Fanning,  Wegmann,  Mc- 
Masters,  Church,  and  Merriman,  who  are  the  more  modern 
American  writers  on  the  subject. 

The  conditions  on  which  the  stability  of  gravity  dams  are 
calculated  are  : 

1.  The  hydrostatic  principles  involved  in  the  pressure  of  a 
volume  of  liquid  on  an  immersed  surface  ;  the  fact  that  this 
pressure  is  perpendicular  to  the  surface  ;  and  that  for  rectangu- 
lar surfaces  it  may  be  considered   as  a  single    force    applied 
below  the  water  surface  at  a  distance  equal  to  -f  of  its  depth. 

2.  That  a  gravity  dam  may  fail:   I,  by  sliding  on  a  hori- 
zontal  joint ;    2,  by  overturning ;    or   3,    by  crushing  of   the 
masonry  or  foundation. 

The  stability  of  the  dam  against  its  liability  to  destruction, 
as  enumerated  in  condition  2,  page  249,  must  be  determined — 

1.  When  the  reservoir  is  full;  and, 

2.  When  the  reservoir  is  empty. 

These  two  conditions  give  the  extreme  positions  of  the 
lines  of  pressure  in  a  dam.  The  first  causes  the  maximum 
pressure  in  any  horizontal  plane  to  be  at  the  down-stream  face 
of  the  wall,  and  the  second  produces  them  at  the  up-stream  face. 
When  the  reservoir  is  empty  the  wall  supports  only  its  own 
weight,  but  if  the  wall  has  a  uniform  thickness  the  pressure  per 
square  inch  will  be  about  85  pounds  if  the  height  of  the  struc- 
ture is  85  feet.  If  the  faces  be  inclined  so  as  to  reduce  the 
mean  thickness,  the  pressure  on  the  base  diminishes  and  the 
height  can  be  accordingly  increased.  From  this  it  is  clearly 
seen  that  it  is  absolutely  necessary  to  widen  the  base  of  the 
dam  by  inclining  its  faces  if  the  wall  is  to  have  any  great  height ; 
otherwise  it  would  rupture  from  the  pressure  of  the  material 
composing  its  own  mass.  When  the  reservoir  is  full,  however, 
the  water  contained  in  it  bears  upon  the  up-stream  face  with  a 
pressure  that  increases  with  the  square  of  the  depth.  In  deep 
reservoirs  this  pressure  is  great,  and  exerts  its  effect  in  a  re- 
sultant which  is  nearly  horizontal  in  direction  and  carries  the 


STABILITY  OF  MASONRY  DAMS. 


251 


maximum  load  to  the  down-stream  toe  of  the  wall.  For  sta- 
bility this  resultant  must  pierce  the  base  in  front  of  this  lower 
edge.  From  these  considerations  arises  the  necessity  of  giving 
the  down-stream  face  a  greater  batter  than  the  up-stream  face. 
The  tendency  of  the  water  pressure  to  produce  overturning 
or  sliding  and  the  weight  of  the  material  are  greater  for  each  suc- 
cessive layer  of  the  mass  of  the  dam  from  the  top  downwards. 
As  a  result  of  this  the  width  of  the  dam  at  the  top  might 
theoretically  be  nil,  and  should  be  increased  downwards  in  such 
a  proportion  as  to  render  the  dam  capable  of  resisting  tenden- 
cies to  crushing,  sliding,  and  overturning.  From  theoretical 
examinations  of  the  effects  of  these  forces  it  has  been  found, 
keeping  constantly  in  view  the  necessity  of  making  the  batter 
of  the  down-stream  face  the  greater,  that  the  dam  should  have 
a  triangular  profile,  somewhat  similar  to  that  represented  in 
Fig.  71. 


FIG.  71. — THEORETICAL  TRIANGULAR  CROSS-SECTION  OF  DAM. 

247.  Stability  against  Sliding. — The  tendency  of  the 
water  pressure  to  slide  any  portion  of  the  dam  forward  on  a 
given  horizontal  plane  is  resisted  by  the  friction  due  to  the 
weight  of  the  mass  above  it.  The  dam  is  necessarily  founded 


252  MASONRY  DAMS. 

on  firm  rock  the  disintegrated  and  weaker  portions  of  which 
must  be  removed,  and  as  a  result  the  base  is  usually  sufficiently 
rough  to  offer  considerable  resistance  to  sliding.  If  this  is  not 
the  case  steps  must  be  cut  for  a  few  feet  in  depth  in  the  foun- 
dation rock,  or  this  must  be  irregularly  cut  in  such  manner  as 
to  leave  trenches  in  which  projections  of  the  dam  will  fit.  The 
dam,  if  properly  constructed,  is  safe  against  any  liability  to 
slide  providing  its  profile  is  such  that  it  will  resist  overturning  ; 
therefore  the  usual  computations  entered  into  to  determine 
whether  it  will  resist  sliding  are  practically  unnecessary.  If  it 
be  constructed  of  rough  rubble  masonry  without  regular  beds, 
and  so  built  as  to  form  a  monolithic  mass,  sliding  is  impossible. 
It  is  well  known  that  the  force  required  to  make  two  pieces  of 
smooth  stone  slide  upon  each  other  when  dry  or  joined  by 
fresh  mortar  is  equal  to  about  .75  of  the  normal  pressure. 
Hence  sliding  would  only  be  possible  when  the  horizontal  was 
equal  to  £  of  the  sum  of  the  vertical  pressures.  In  none  of  the 
formulas  or  profile  types  ordinarily  employed  is  the  ratio  of 
the  thrust  to  the  pressure  beyond  .7,  while  it  more  ordinarily 
ranges  between  .3  and  .5 

248.  Coefficient  of  Friction  in  Masonry. — In  the  follow- 
ing table  are  given  the  coefficients  of  friction  in  dry  masonry 

of  various  kinds : 

TABLE  XII. 

COEFFICIENTS   OF   FRICTION   IN   MASONRY. 

Coefficient. 

Point-dressed  granite  on  like  granite 70 

Point-dressed  granite  on  brick 63 

Point-dressed  granite  on  smooth  concrete. 62 

Fine-cut  granite  on  like  granite 60 

Fine-cut  granite  on  be"  ton  block 60 

Dressed  granite  on  granite  with  fresh  mortar 50 

Beton  blocks  on  b£ton  blocks 65 

Common  brick  on  common  brick 65 

Common  brick  on  common  brick  with  wet  mortar 50 

Common  brick  on  dressed  limestone 60 

Dressed  hard  limestone  on  limestone 65 

Dressed  soft  limestone  on  like  limestone 75 


COEFFICIENT  OF  FRICTION  IN  MASONRY.  2$$ 

According  to  J.  T.  Fanning,  let 

6"  =  the  symbol  of  friction  of  stability; 

x  =  the  horizontal  water  pressure  resultant  ; 

c  =  the  coefficient  of  friction  of  the  given  section  ; 
w  =  the  weight  of  masonry  above  that  section  ; 

e  =  the  vertical  downward  water  pressure  resultant  ; 

z  =  the  maximum  upward  water  pressure  resultant  ; 
c1  =  the  ratio  of  effective  upward  water  pressure  to  the  maxi- 
mum. 

Then,  when  5  and  x  are  equal  to  each  other,  the  wall  is  on 
the  point  of  motion  and  5  must  be  increased.  This  has  to  be 
done  by  adding  more  weight  to  the  wall.  This  weight  should 
be  increased  until  it  is  able  to  resist  a  thrust  of  at  least  1.5^, 
when 


The  wall  has  a  small  margin  of  fractional  stability  when 
x  —  2.2$  tons.  Ordinarily  the  weight  or  pressure  of  the  wall 
far  exceeds  this  figure,  and  is  usually  from  5  to  12  tons  per 
square  foot.  For  equilibrium,  let 

x  <  cw  -{-  ml, 

in  which  m  is  the  cohesion  of  the  masonry  per  square  unit  and 
/  the  length  of  the  joint  at  the  section  above  x.  The  value  of 
m  is  so  considerable  that  ml  may  be  considered  as  a  margin  of 
safety,  when  we  have  x  =  cw.  To  find  what  value  of  c  will 

x 
prevent  sliding,  we  have  c  =  -  . 

A  masonry  wall  must  be  founded  upon  solid  rock  which  is 
either  naturally  uneven  or  must  be  made  so,  and  it  must  be 
made  of  rubble  masonry  or  concrete  not  laid  in  courses.  As 
there  can  therefore  be  no  smooth  planes  to  slide  one  upon 


254  MASONRY  DAMS. 

the  other,  the  coefficient  of  friction  in  the  mass  must  be 
many  times  the  superincumbent  weight  ;  and  we  may  con- 
clude, therefore,  that  there  is  no  possible  danger  of  failure  from 
sliding. 

249.  Stability  against  Crushing. — According  to  the 
method  given  by  Debauve,  when  the  reservoir  is  full  and  the 
resultant  of  the  pressure  of  the  water  and  the  weight  of  the 
masonry  intersects  the  base  at  one  third  of  its  width  from  the 
down-stream  toe,  the  maximum  pressure  is  at  this  toe,  and  is 
double  what  the  pressure  per  square  inch  would  be  if  the 
weight  were  uniformly  distributed  over  the  whole  base.  When 
the  reservoir  is  empty  the  conditions  are  reversed,  the  maxi- 
mum pressure  being  at  the  up-stream  toe  and  equal  to  double 
the  average  pressure  on  the  base. 

From  this  proposition  Mr.  James  B.  Francis  differs.  He 
believes  that  the  pressures  near  the  base  of  the  wall  are  prac- 
tically zero,  and  that  these  pressures  are  transferred  to  the  cen- 
tral part  of  the  mass,  where  the  resistance  to  crushing  is  greatest. 
In  other  words,  that  the  masonry  is  not  perfectly  rigid,  and  that 
it  becomes  accordingly  unnecessary  to  take  account  of  crushing 
pressures  in  a  dam  less  than  200  feet  in  height.  In  this  opinion 
other  authorities  agree  with  Francis  to  a  limited  extent,  though 
all  prefer  to  Calculate  the  limit  of  pressure  in  the  usual  manner, 
namely,  to  measure  the  pressures  near  the  face  of  the  wall,  as 
that  gives  a  safer  factor,  though  it  may  be  unnecessarily  high. 
As  parts  of  the  dam  are  built  at  different  times  in  the  year  and 
under  different  conditions,  the  structure  cannot  be  truly  homo- 
geneous. The  absence  of  fractures  at  the  thin  portion  near  the 
toe  of  the  dam  indicates  the  absence  of  excessive  strains  at  that 
point ;  it  is  therefore  more  probable  that  the  real  point  of  dis- 
tribution of  pressure  lies  somewhere  between  the  extremes 
enumerated  by  Debauve  and  Francis.  Up  to  the  limit  of  200 
feet  in  height  there  is  no  doubt  that  the  crushing  strength  of 
well-laid  masonry  need  not  be  considered. 

The  following,  from  Wegmann,  is  a  brief  synopsis  of  a 
simple  formula  for  finding  the  distribution  of  pressure  at  any 
point  in  a  dam  : 


LIMITING  PRESSURES.  2$$ 

Let  W  =  the  total  pressure  on  the  base  ; 

u  =  the  distance  of  W  from  the  nearest  edge  ; 
/  =  the  maximum  pressure  on  the  foundation  ; 
q  =  the  minimum  pressure  on  the  foundation  ; 
/  =  the  length  of  the  joint  or  base  under  considera- 
tion. 

2  W 

When  u  =—  ,  or  in  other  words  the 


2  W 
pressure  is  within  the  middle  third  of  the  base,  /  =  -—  .     If 

the  pressure  is  without  the  middle  third  there  will  be  tension 
in  the  mass.  As  it  is  unsafe  to  depend  on  the  tension  in 
masonry,  it  would  be  best  to  neglect  this  in  calculating  the 

2\V 

pressure  on  the  foundation,  and  this  will  become  /  —  —  —  .    An- 

other simple  formula  for  determining  the  pressure  on  the  base, 
and  one  which  leads  to  practically  similar  results,  is  the  follow- 
ing, given  by  Ira  O.  Baker: 

W 


250.  Limiting  Pressures.  —  The  limiting  pressures  which 
it  maybe  safe  to  permit  in  masonry  differ  considerably  accord- 
ing to  various  authorities.  From  actual  tests  these  pressures 
differ  according  to  the  dimensions  of  the  masonry  blocks,  and 
it  is  probable  that  much  greater  pressures  can  be  sustained  per 
unit  of  area  in  the  interior  of  large  masses  than  in  the  smaller 
experimental  blocks  or  near  the  surface  of  the  mass.  The  fol- 
lowing pressures  are  ordinarily  accepted:  Brick,  120  pounds; 
sandstone,  130  pounds;  limestone,  152  pounds;  granite,  155 
pounds  per  square  inch.  It  is  not  advisable  to  allow  either  a 
direct  or  resultant  pressure  exceeding  140  pounds  per  square 
inch  within  I  foot  of  the  face  of  rubble  masonry  or  exceeding 
200  pounds  per  square  inch  in  the  heart  of  the  work.  On  some 
of  the  great  structures  already  built  limits  of  pressure  as  low  as 
85  pounds  have  been  adhered  to,  while  pressures  exceeding  200 


256  MASONRY  DAMS. 

pounds  per  square  inch  have  been  permitted  in  the  Almanza 
and  the  Gros  Bois  dams  in  Europe. 

Among  the  great  dams  which  have  been  constructed  the 
pressures  vary  between  5.8  tons  per  square  foot  in  the  Verdon 
dam  in  France  and  14.6  tons  per  square  foot  in  the  Gros  Bois 
dam,  while  the  proposed  Quaker  Bridge  dam,  in  New  York,  was 
designed  for  a  maximum  pressure  of  16.6  tons  per  square  foot. 
It  is  probable,  however,  that  a  safe  average  limit  is  that  already 
given  of  from  140  to  200  pounds  per  square  inch. 

251.  Stability  against  Overturning. — To  insure  ample 
safety  against  all  the  causes  of  failure  in  a  dam  in  addition  to 
the  other  conditions  already  fixed,  the  lines  of  pressure  must 
lie  within  the  centre  third  of  the  profile,  whether  the  reservoir 
be  full  or  empty.  This  last  condition  precludes  the  possibility 
of  tension,  and  insures  a  factor  of  safety  of  at  least  two  against 
overturning.  In  Fig.  72  suppose  the  lines  of  reaction  R  and 

H 


l 


FIG.  72.  —  DIAGRAM  ILLUSTKATING  WEGMANN'S  FORMULA. 

W  to  intersect  the  joint  /  at  the  limit  of  its  centre  third. 
Taking  the  moments  of  the  three  forces,  H,  R,  and  W,  which 

Hd      Wl 
are  in  equilibrium  at  about  the  point  e,  we  find  --  =  —  ,  in 

o  o 

which  d  =  the  depth  of  water  at  the  joint  above  the  plane 
of  /.  If  the  moments  are  taken  about  the  front  edge  a,  the 
lever  arm  of  ^will  be  double,  while  that  of  H  remains  un- 
changed ;  the  factor  of  safety  against  overturning  is  therefore 
two.  It  is  equally  evident  that  if  the  line  of  reaction  of  W  or 
R  should  intersect  /within  its  centre  third,  the  factor  of  stabil- 
ity would  be  greater  than  two. 


STABILITY  AGAINST  OVERTURNING. 

The  following  formulas  are  taken  from  the  treatise  of 
Edward  Wegmann,  Jr.,  on  Masonry  Dams,  because  the  author 
considers  them  simple  and  accurate.  For  their  deduction; 
and  discussion  the  student  should  refer  to  this  work.. 
The  mass  of  the  cross-section  of  the  dam  should  be 
rectangular  and  will  contain  an  excess  of  material  as  regards 
resistance  to  the  hydrostatic  pressure  of  the  water  ;  P  will  pass 
through  the  centre  of  the  rectangle,  and  P  will  gradually  ap- 
proach the  front  face  eventually  reaching  some  joint  x  =  a 

where  u  =  —  .     The  depth  of  this  joint  below  the  top  of  the 

«J 

dam  is  d  =  a  Vr,  where 

P=  the  line  of  pressure,  reservoir  full  ; 
P'  =  the  line  of  pressure,  reservoir  empty; 

x  =  the  unknown  length  of  the  joint  ; 

u  —  the  distance  of  P  from  the  front  edge  of  the  joint  x  ; 

a  —  the  top  width  of  the  dam  ; 

d—  the  depth  of  water  at  the  joint  x\ 

r  =  the  specific  gravity  of  the  masonry. 

For  the  next  course  below  the  joint  x,  where  the  dam- 
begins  to  assume  a  trapezoidal  cross-section,  we  have 


in  which  w  =  equals  the  total  weight  of  masonry  resting  on 
the  joint  /. 

/  =  the  known  length  of  the  joint  above  x  ; 

h  =  the  depth  of  a  course  of  masonry^  assumed  as  10  feet  ; 

m  =  the  distance  of  P'  from  the  back  edge  of  the  joint  /; 

d* 
M  —  -7—  =  the  moment  of  H  on  the  joint  x  ; 

d? 

H  =  —  =  the  horizontal  thrust  of  the  water. 
2r 

Equation  (2)  may  be  used  for  a  series  of  joints  down  to  a 
depth  where  the  back  surface  of  the  dam  begins  to  slope  or  until 

a  joint  is  found  where  n  =  -  ;  n  being  the  distance  of  P'  from 


258  MASONRY  DAMS. 

the  back  edge  of  the  joint  x.     For  the  next  course  both  faces 

x 
will  have  to  be  sloped,  and  u  =  n  —  —  ,  when  we  obtain 

6M 


In  applying  equation  (3)  for  finding  the  value  of  x>  the 
maximum  pressure  must  be  obtained  both  with  reservoir  full 
and  empty.  This  may  be  done  by  the  formula 

6M 


in  which  /  =  the  limiting  pressure  per  square  foot  at  the 
front  face  of  the  dam.  This  equation  may  be  employed  until 
the  limiting  pressure  is  reached  at  the  back  face,  when  the 
following  formula  must  be  used  : 


2*™  +        =6M>  •     •     -     (5) 

in  which  q  is  equal  to  the  limiting  pressure  per  square  foot  at 
the  back  face  of  the  dam,  and  is  generally  assumed  to  be  greater 
than  /. 

These  equations  give  the  successive  lengths  of  the  joints, 
but  do  not  give  their  position.  This  may  be  found  by  deter- 
mining the  value  of  y  =  the  batter  of  the  back  face  ;  the 
formula  being 


_ 
and  for  equation  (5), 


-  6m)  +  lh(x  - 


The  theoretical  profile  resulting  from  calculating  the  dam 
by  the  above  formulas  will  have  polygonal   faces.     It   only 


MOLESWORTH'S  FORMULA    AND   PROFILE    TYPE.      2 59 

becomes  necessary  then  to  make  the  value  of  h  sufficiently 
small  to  determine  a  profile  with  a  smooth  surface  which  will 
fulfil  all  of  the  conditions. 

252.  Molesworth's  Formula  and  Profile  Type.— Mr. 
Guilford  L.  Molesworth  has  worked  out  the  following  formula, 
the  application  of  which  gives  the  profile  shown  in  Fig.  73 : 


§8 


M.    W. 


-^-^i-q^-  ~=*^=-=- 

\A  \_                     «  t  y  <rf  -J  ;  fr  s  •*  a,-  ye(;.«jc  asa.mtnunuo» 

FH  —  »•  i      - 

to;ii    H 

CQ  i  i     j  J 

IT 

i  i  i     j 

•\\\                     H  *  HtLfht  of  o<un  ,n  feet 

i  i  i    ! 

•V«\\                    Z-OtFt-h^fcitofanyhoritontat.pta.nitotoitlf.IKU 

:  j 

7-ey.J.  %1  \\2                ^  *  <^S*f  '"  feetfrom  t*r*fca(  Line,  A  A  to  OUttf  foft  of 

\  U\\                a'a/77  ^««y  <^^  or; 

00.' 

',   \'«<    \\            2s.0ffsettouinerfcu:e- 

601! 

i   \  \    '\\                 *  =  Width  in  feet  of  dam  at  top; 

jf 

r  "-^|  -V^'3^5           A  =  ^m/f  <jc  P/x«a^/^  7b«>o»r  SfHW/ort 
\     '-^       \ 

8 

•oil      i    «« 

-""T\|/9'7\* 

"ft          —  ***^ 

00;  1 

^      Vl                  X 

i  i 

lOQl-i  _                          fjM. 

-V9+.  ^'r  -  -  V  J.1  -  -  30.80-  -\A« 

1    %              \ 

*\      \  •*               X 

Tt             ^T 
woH 
:  |               I 

V.            \>o                                X 

I2<tr-r  fc*JB- 
'•  1                              / 

--  «*.;*__,£-  1^.__.«.73  '--NM* 

\     \               x 

J 

tTOj-J»^—  —  —  •  7.493'-  — 

yL,l. 

—  »«-  ---?."  "4  -»»  "\^8* 

w-^ii-4f       *<30 

*«*  » 

FIG.  73. — MOLESWORTH'S  PROFILE  TYPE. 


^  = 


.05*- 


+  (.03*) 


^  =  the  distance  measured  along  any  joint  in  the  masonry 
from  the  down-stream  face  to  a  vertical  line  drawn 
from  the  top  front  edge  of  the  dam  to  the  base  ; 

8  =  the  corresponding  distance  on  the  same  joint  to  the  up- 
stream face  ; 


200  MASONRY  DAMS. 

x  —  the  distance  from  the  top  of  the  dam  to  the  joint  above 

mentioned ; 

y  —  .6-*-  as  a  minimum  ; 
\  =  the  limit  of  pressure  of  the  masonry  in  tons  per  square 

foot; 
H  —  the  minimum  height  of  dam  ; 

TT 

a  =  y  at  —  from  the  top ; 
4 

b  =  top  width  =  -. 

253.  Height  and  Top  Width   of  Dam. — As  far  as  the 
forces  already  considered  are  concerned,  the  top  width  of  the 
dam  might  be  zero  and  the  water  might  rise  to  its  crest.     In 
practice  a  certain  definite  top  width  must  be  given  in  order  to 
enable  the  dam  to  withstand  the  shock  of  waves  and  ice,  and  the 
top  of  the  dam  must  be  continued  above  the  maximum  flood- 
water  line  for  a  sufficient  height  to  prevent  its  being  topped 
by  waves.     Ordinarily  the  top  width  of  the  dam  should  be 
sufficient  to  enable  it  to  act  as  a  roadway  and  afford  commu- 
nication between  the  two  slopes  of  the  valley.     It  should  never 
be  less  than  5  or  6  feet,  and  for  the  highest  dams  need  never 
exceed  15  feet,  varying  between  these  according  to  the  height 
of  the  wall. 

Having  calculated  the  height  of  the  dam  for  maximum  flood 
heights  of  water,  this  should  be  continued  upward  a  sufficient 
amount  to  insure  it  against  being  topped  by  the  waves.  The 
height  of  waves  depends  on  complex  causes,  chiefly  on  the 
depth  of  the  reservoir  and  the  fetch,  a  formula  for  computing 
which  was  given  in  Article  237.  The  maximum  amount  to 
which  it  will  be  necessary  to  increase  the  computed  height  of 
the  dam  need  rarely  or  never  exceed  10  feet,  its  minimum  being 
as  low  as  one  foot  in  an  extremely  shallow  and  small  reservoir. 
On  top  of  the  crown  of  the  dam  there  should  always  be  a  para- 
pet as  an  additional  precaution  against  its  being  topped  by 
waves,  and  this  parapet  may  be  from  3  to  5  feet  in  height. 

254.  Profile  of  Dam. — In  Fig.  74  is  given  a  comparison  of 
the  profiles  obtained  by  several  of  the  more  common  formulas, 


PROFILE   OF  DAM. 


26l 


while  that  which  is  shown  in  full  lines  is  the  practical  profile 
type  No.  3,  adopted  by  Wegmann.  This  profile  (Fig.  75)  can 
be  changed  to  another  having  any  desired  top  width  equal  to 
one  tenth  the  height  by  simply  changing  the  scale  of  the 


SCALC  OF  FttT 
0  5  10     30     30    40     SO     60    70 


DELOCRES  TYPE* 

_:_« RAHKIMC'S      „' 

_ KRANTZ'S 

'. „•._  CRU6HOLAS  .. 

I.  QUAKER  BRIDGE  OA 

_'  PROPOSED  TYPEA 


\ 


FIG.  74. — COMPARISON  OF  PROFILE  TYPES. 

drawing.  In  the  following  table  are  given  the  dimensions  and 
pressures  for  this  profile  type.  The  specific  gravity  of  the 
masonry  employed  in  making  these  computations  is  assumed 
at  2^. 

255.  Curved  Masonry  Dams. — A  dam  of  the  kind  already 
considered  is  of  the  pure  gravity  type  and  relies  for  its  sta- 
bility solely  on  the  weight  of  the  masonry  and  its  friction.  A 


262 


MASONRY  DAMS. 


•ranuqnmbg 
joj  AjKssaoau  uop 
uj  jo  ' 


8O  co  rf  co  O  U->O>H   d   co  co  co  co  co  Ol    M   O   OGO  O 
M   M   co  "^-  to  in  u->o  OOOOOOOOO   inmtn 

6  6  6.6  6  6  6  6  6  6  6  6  6  6  6  6  6  6  6  6  6 


1-1  O  CO  CO    O    vnO    Tj-  N  CO    vr>  CO  -1-QO    •"tf-CO  CO    >•«  CO    CO 

r^coomwo  WvO  O  •<!•  o  rj-  .-I  H.  M  en 


M  M  a  co  "3- 


co  coooooo 


o  <3-  w  coco 


co  -t-  rj-  o  o  w 


COCO    CO  O" 

M  •-*  N  es 


O  i^  f^  r^oo  oocococococoooco 


8Oi^r-«cOMMTtcOMcor^Tj-ot-"'-<NxncoNO 
•H  coco   o^l-i^co  woo  coco  cooma  o   rtoinrf 


OO    NO    O 

0s  9>  O  O  *i 


ui  ' 


-<i-r^t-<covc  coo 


-SS3Jd  JO  3UJI  05  30BJ 
1UOJJ  UIOJJ  30UH?SIQ 


co  co  O^O  r^O 
Ooo  t>«  r>-co  6 


~>   MOO  r--O  moo   o^  ex  *-•  r}-co  m 
'^•O   «   O   co  M    ^MO   t^inN    O>t-> 

rj-o  o  c<  u-i  a>  coco  co  t^o  -^-  ci  a 


cotn»nc>O 


couic>ao   rfO 


inTtoo   Oco  oo   M 
t^r>.co  u->vn^i-io  »noo  inr^ 

CO  CO*  CO    6    T   OO    N    OO 

' 


O^O 
>-iO 


r^co  oo  ^ 


SOOO 
O  O  O 


t^r^coco  M 

^-  mo  r^  M  o 


"i    M    a    <N 


N   xnM   t-i 


M   ^-1-1  M 


CO  Tt  CO  1-1 


cooooo   O   •^f 
M>-.i-.NN 


OO   vr>O   t^ON 
-cooOi-iNcotnv 


jo  jaaj  oiqno 


co  m  O  m  O  ^"  m  m  O   ^t"  O   ^  O  O   O   m  O  *o  O  ^t" 

MTtoomTl-OW    MincoOO    >-I<N    OO    OM 

M   cs   cotr>r^OM   xoO^tOu-ii-cco  i^ 

M  M  M  c«  ei  (O  ^t-^  in 


•XJUOSBJ^  jo  133J 
jo 


O   OO    cocovn«-i    OO   ^t«    i-" 


'^oo    Ncooo   O   m 

Oco  >-i  OI-ICGCO  cocoo 
*-co  ~f  >->  Or>>u-> 
'^-'^  vr>O  O  r~CO 


•}33J    UI 

'tnep  jo  do^  MO\ 


OOOOOOOOOOOOOOOOOOOOO 
M  w  cOTfino  r^co   OO  >->  N  coTinvo  t^oo  OO 


CURVED  MASONRY  DAMS. 


263 


dam  of  the  pure  arched  type  relies  solely  on  the  arched  form 
for  stability,  in  which  case  the  pressure  of  the  water  is  trans- 
mitted laterally  to  the  abutments.  If  our  knowledge  of  the 
laws  governing  masonry  arches  were  more  complete,  the 
arched  or  curved  dam  would  probably  be  the  best  type,  since 


•SCALE    OF    FEET 
0    5    10    IS 


19098 

FIG.  75.— PRACTICAL  PROFILE  FROM  WHGMANN. 

it  will  contain  the  least  amount  of  material.  As  it  is,  we  know 
something  of  the  laws  governing  such  true  masonry  arches 
as  those  supporting  bridges.  In  thece  the  two  extremities  of 
the  arch  are  raised  at  their  springing  on  some  firm  abutment 


264  MASONRY  DAMS. 

and  the  whole  is  keyed  together  at  the  centre ;  but  in  a 
masonry  dam  of  arched  form  not  only  is  the  arch  supposed  to 
transmit  the  pressures  laterally  to  the  side  of  the  abutments, 
but  as  the  dam  rests  on  the  bottom  of  the  valley  it  is  sus- 
tained again  at  that  point,  so  that  it  cannot  act  as  a  true  arch, 
— nearly  perfect  arch  action  only  occurring  at  the  top,  where 
the  pressure  is  a  minimum,  while  near  the  bottom,  where  the 
pressure  is  greatest,  probably  very  little  of  this  is  transmitted 
to  the  abutments.  For  this  reason  it  is  not  yet  considered 
safe  to  build  a  dam  depending  purely  on  the  arched  form,  and 
such  few  dams  as  have  been  constructed  on  this  principle  have 
been  given  somewhat  of  the  gravity  cross-section,  increasing 
downward  in  width,  so  that  they  presumably  resist  the  press- 
ure both  by  gravity  and  arch  action.  The  three  best  existing 
types  of  such  works  are  the  Zola  dam  in  France  and  the  Bear 
Valley  and  Sweetwater  dams  in  California  (Arts.  275  and  281). 

That  a  masonry  dam  constructed  across  a  narrow  valley 
can  resist  the  water  pressure  by  transmitting  it  to  its  abut- 
ments is  proved  by  the  dams  above  cited.  The  question  then 
arises,  can  the  profile  be  reduced  from  what  would  be  required 
if  the  plan  were  straight?  As  stated  at  the  beginning  of  this 
chapter,  Krantz  asserts  that  a  dam  curved  in  plan  and  con- 
vexed  up-stream  with  a  radius  65  feet  or  less  will  transfer  the 
pressure  of  the  water  to  its  abutments.  Dams,  however,  of 
even  greater  radius  than  this  do  transfer  the  pressure  to  the 
abutments.  The  radius  of  the  Zola  dam  is  158  feet  and  its 
length  on  top  is  205  feet.  The  length  of  the  Bear  Valley  dam, 
which  depends  almost  wholly  on  its  arched  form  for  its.  sta- 
bility, is  230  feet,  the  radius  at  the  top  being  335  feet  and  at 
the  bottom  226  feet.  The  Sweetwater  dam  is  380  feet  in 
length  on  top,  its  radius  at  the  same  point  being  222  feet.  M. 
Delocre  says  that  a  curved  dam  will  act  as  an  arch  if  its  thick- 
ness does  not  exceed  one  third  of  the  radius  of  its  up-stream 
or  convex  side.  M.  Pelletreau  fixes  the  limiting  value  of  the 
thickness  at  one  half  of  this  radius.  When  a  dam  acts  as  an 
arch  it  only  transmits  the  water  pressure  to  the  sides  of  the 
valley;  its  own  weight  must  still  be  borne  by  the  foundation. 


DESIGN  OF  CURVED  DAMS.  26$ 

256.  Design  of  Curved  Dams.  —  Mr.  Wegmann  gives  th2 
following  formula  for  calculating  the  thrust  in  curved  dams  of 
circular  plan  : 


in  which  /  =  the  uniform  thrust  in  the  circular  rings  of  any 

plane  of  the  masonry  ; 
/  =  the  pressure  per  unit  of  length  of  this  section  of 

the  ring  ; 
r  =  the  radius  of  the  rings  of  the  outer  surface. 

Arch  action  can  only  take  place  by  the  elastic  yield  of  the 
masonry  ;  but  little  is  known  of  the  elasticity  of  brick,  stone, 
etc.,  and  nothing  of  the  elasticity  of  masonry;  hence  it  is  im- 
possible to  determine  the  amount  of  the  arch  action. 

It  may  be  shown  theoretically  that  in  the  case  of  a  narrow 
valley  a  profile  of  less  area  may  be  employed  for  a  dam  which 
is  curved  in  plan  than  one  in  which  the  plan  is  straight.  An 
excellent  theoretical  discussion  of  this  subject  has  been  pub- 
lished by  Messrs.  Hubert  Vischer  and  Luther  Wagoner.  The 
result  of  the  investigations  of  these  gentlemen  goes  to  show 
that  arch  action,  as  usually  understood,  adds  little  to  the 
strength  of  a  curved  dam.  Notwithstanding  this,  the  curved 
form  may  to  a  marked  degree  afford  additional  resistance, 
and  this  in  a  manner  less  dependent  on  the  radius  of  the 
curve  than  the  arched  theory  implies.  The  general  conclusion 
reached  by  these  gentlemen  is,  further,  that  the  rate  of  effi- 
ciency of  a  curved  dam  over  the  straight  decreases  with  the 
increased  length  of  the  dam  ;  that  very  narrow  cross-sections 
are  not  justifiable  ;  and  they  ascribe  the  high  duty  of  the  Bear 
Valley  dam  to  a  favorable  combination  of  conditions  which 
could  not  have  held  good  if  the  span  had  been  considerably 
longer  or  the  workmanship  less  excellent. 

Engineers  are  now  generally  agreed  upon  the  advantages 
of  the  curved  plan.  Its  chief  disadvantage  is  the  increased 
length  of  the  dam  over  a  straight  plan,  and  the  consequent 
increase  in  the  amount  and  cost  of  material  to  within  certain 
limits  of  top  length  and  radius.  Though  the  cross-section  of  a 


266  MASONRY  DAMS. 

curved  dam  should  unquestionably  be  somewhat  reduced,  it 
would  be  unsafe  to  reduce  it  as  much  as  has  been  done  in  the 
case  of  the  Bear  Valley  and  Zola  dams,  though  these  have 
withstood  securely  the  pressures  brought  against  them.  It 
might  with  safety  be  reduced  to  the  dimensions  of  the  Sweet- 
water  dam,  thus  saving  largely  in  the  amount  of  material  em- 
ployed. All  of  the  more  conservative  writers,  as  Wegmann, 
Rankine,  and  Krantz,  recommend  that  the  design  of  the 
profile  be  made  sufficiently  strong  to  enable  the  wall  to  resist 
water  pressure  simply  by  its  weight,  and  to  curve  the  plan  as 
an  additional  safeguard  whenever  the  topography  makes  it 
advisable.  American  engineers,  and  especially  those  of  the 
West,  however,  are  prone  to  be  more  liberal ;  and  the  tendency 
is  toward  a  slight  reduction  in  the  cross-section  where  a  curved 
plan  is  practicable.  An  additional  advantage  of  the  arched 
form  of  dam  is  that  the  pressure  of  the  water  on  the  back  of 
the  arch  is  perpendicular  to  the  up-stream  face,  and  is  decom- 
posed into  two  components,  one  perpendicular  to  the  span  of 
the  arch  and  the  other  parallel  to  it.  The  first  is  resisted  by 
the  gravity  and  arch  stability,  and  the  second  thrusts  the 
up-stream  face  into  compression,  which  has  a  tendency  to 
close  all  vertical  cracks  and  to  consolidate  the  masonry  trans- 
versely. 

An  excellent  manner  in  which  to  increase  the  efficiency 
of  the  arch  action  in  a  curved  dam  is  that  employed  in  the 
Sweetwater  and  Buchanan  reservoir  dams,  the  latter  of  which 
has  recently  been  designed  for  construction  in  California. 
This  consists  in  reducing  the  radius  of  curvature  from  the 
centre  towards  the  abutments.  The  good  effect  of  this  is  to 
widen  the  base  or  spring  of  the  arch  at  the  abutments,  thus 
giving  a  broader  bearing  for  the  arch  on  the  hillsides.  In  the 
Sweetwater  dam  the  effect  of  this  is  seen  in  projections  or 
rectangular  offsets  made  on  the  down-stream  face  of  the  dam 
(PL  XXIV),  the  centre  of  the  dam  sloping  evenly,  while  the 
surface  is  broken  by  steps  where  it  abuts  against  the  hillside. 
In  the  Buchanan  dam,  the  length  of  which  is  780  feet  on  top, 
the  maximum  radius  at  the  centre  is  1146  feet,  and  this  is 


FOUNDATIONS.  267 

diminished  gradually  to  736  feet  at  the  abutments.  These 
changes  in  the  radii  are  made  gradually,  and  are  not  shown  in 
the  surface  of  the  dam  in  projections,  as  the  entire  outer  surface 
is  smoothed  off  evenly. 

257.  Foundations. — Masonry  dams  must  be  founded  on 
solid  rock,  and  great  care  and  judgment  are  required  in  deter- 
mining just  when  the  excavation  for  the  foundation  has  pro- 
ceeded sufficiently  far.     If  the  looser  and  partially  decomposed 
surface  rock  is  not  entirely  removed  there  is  danger  of  leakage 
under  the  dam,  and  consequent  liability  of  its  destruction.     If 
the  excavation  is  carried  too  far  into  the  underlying  rock  much 
money  may  be  wasted.     Frequent  cases  might  be  cited  where  it 
has  been  found  necessary  to  make  unusually  deep  excavations  in 
order  that  a  sufficiently  firm  foundation  might  be  reached.     In 
the  case  of  the  Turlock  dam  the  average  depth  of  excavation  in 
the  large  bowlders  and  underlying  porphyry  was  from  5  to  10 
feet  to  the  homogeneous  material.     In  one  or  two  cases,  how- 
ever, seams  full  of  huge  bowlders  weighing  several  hundred  tons 
apiece  were  encountered,  which  necessitated  excavation  to  a 
depth  of  25  to  35  feet  in  order  that  they  might  be  worked  out 
and  homogeneous  rock  reached.     A  masonry  dam  is  an  abso- 
lutely rigid  structure,  and  the  least  unequal  settlement  in  any 
portion  of  it  tends  to  produce  a  crack.    A  clay  or  hardpan  foun- 
dation is  almost  sure  to  yield  under  the  weight  of  a  masonry 
dam,  and  be  the  loose   material  ever  so  little  in  amount,  if  it 
offers  opportunity  for  subsidence  it  will  result  in  the  rupture  of 
the  dam.     The  safe  load   on  the  lower  courses  of  a  masonry 
dam  depends  on  the  character  of  the  material  of  which  it  is 
composed,  and  may  reach  from   10  to  15  tons  per  square  foot, 
and   nothing  but   the  most  substantial  rock  will  bear  such  a 
weight  as  this. 

258.  Material  of  which  Constructed. — Ashlar  Masonry. 
— Reservoir  dams  may  be  built  of  cut  masonry,  of  rubble  or 
concrete    with    dressed-stone    facing,    or    of    random    rubble. 
The  first  would  be  the  best  for  the  purpose  on  account  of  its 
strength,  but  while  only  twice   as   strong  as  rubble,  it  costs 
three  or  four  times  as  much.     As  the  form  of  the  upper  part 


268  MASONRY  DAMS. 

of  the  dam  depends  on  the  positions  of  the  lines  of  pressure 
and  not  on  the  strain  in  the  masonry,  the  great  strength  of  cut- 
stone  work  would  only  avail  in  the  lower  portion  of  the  dam. 
Great  care  would  have  to  be  employed  in  the  use  of  cut  ma- 
sonry in  order  that  it  should  not  be  laid  in  horizontal  beds, 
which  might  permit  of  shearing  or  sliding,  and  in  order  that 
it  should  break  joints  with  a  proper  degree  of  irregularity. 
Neither  the  vertical  nor  the  horizontal  joints  in  a  dam  should 
be  continuous  ;  therefore  if  made  of  cut  or  ashlar  masonry  or 
of  square  stone  the  joints  should  be  carefully  broken. 

Rubble  or  concrete  with  cut-stone  facing  is  not  a  desirable 
material  of  which  to  construct  a  dam,  because  of  the  difference 
in  settling  of  the  two  kinds  of  masonry,  which  might  result  in 
the  formation  of  cracks  and  seams.  Where  the  facing  becomes 
detached  in  this  manner  from  the  remainder  of  the  body  of  the 
wall  the  strength  of  the  structure  is  reduced  to  that  of  the 
uncoursed  or  concrete  centre.  The  most  prominent  examples 
of  the  use  of  cut-stone  facing  with  rubble  or  concrete  interior 
are  to  be  found  in  the  Vir,  Bhatgur,  and  Betwa  dams  of  India, 
which  are  briefly  described  in  Articles  270  and  277,  and  the 
new  Croton  dam  in  New  York  (Art.  271).  In  each  of  these 
the  cut  stone  is  laid  as  headers  and  stretchers,  and  the  former 
are  well  bonded  into  the  mass  of  the  dam.  The  use  of  this 
form  of  construction  is  condemned  by  many  Indian  engineers, 
and  is  not  approved  in  this  country. 

259.  Concrete. — Some  engineers  consider  concrete  too 
pervious  a  material  to  be  placed  in  a  dam.  It  has,  however, 
been  successfully  employed  in  four  of  the  greatest  dams  yet 
constructed,  namely,  the  San  Mateo  dam  in  California,  170  feet 
in  height;  the  Periar  dam  in  India,  155  feet  high  ;  and  in  the 
Geelong  and  Betaloo  dams  in  Australia,  respectively  60  and 
no  feet  in  height  (Articles  272-274).  The  Periar  and  Betaloo 
dams  are  two  of  the  best  examples  of  the  homogeneous  use  of 
concrete.  The  great  disadvantage  in  using  this  material,  aside 
from  engineering  considerations,  is  the  added  cost  of  cement 
where  the  latter  is  expensive.  The  great  advantage  of  the 
use  of  concrete  and  that  which  determined  its  employment  in 


CONCRETE.  269 

the  Periar  dam  is  the  saving  effected  in  labor;  for  concrete 
can  be  mixed  and  handled  entirely  by  machinery  worked  by 
water-power  furnished  by  the  reservoir  while  under  construc- 
tion. In  the  Beetaloo  dam  for  46  feet  above  the  founda- 
tion the  concrete  was  made  of  one  part  Portland  cement,  two 
parts  washed  sand,  and  four  parts  broken  stone  of  2-inch 
gauge.  In  building  the  structure  great  care  was  taken  to  have 
the  surface  of  the  set  concrete  picked,  washed,  and  brushed 
before  a  fresh  layer  was  deposited,  and  the  new  concrete  was 
kept  shaded  from  the  sun  while  setting.  This  dam  was  built 
up  as  a  monolithic  mass,  the  concrete  being  laid  between 
boards  or  framing  bolted  in  the  body  of  the  dam.  After  re- 
moval these  boards  left  their  imprint  on  the  sides  of  the  struc- 
ture, which  marking  still  remains. 

In  choosing  concrete  as  the  material  to  be  employed  in  the 
construction  of  the  Periar  dam  in  India  the  engineer  held  that 
concrete  is  nothing  more  than  uncoursed  rubble  reduced  to  its 
simplest  form.  As  regards  resistance  to  crushing  or  percola- 
tion, he  holds  that  the  value  of  the  two  materials  is  identical, 
unless  it  be  considered  as  a  point  in  favor  of  concrete  that  it 
must  be  solid,  while  rubble  may,  if  the  supervision  be  defective, 
contain  void  spaces  not  filled  with  mortar ;  he  holds  that  the 
selection  between  the  two  depends  entirely  on  their  relative 
cost.  The  proportion  of  materials  employed  in  this  dam  were  : 
for  every  100  cubic  feet  of  concrete,  60  cubic  feet  of  solid  stone 
plus  10  per  cent  for  wastage,  25  cubic  feet  of  native  hydraulic 
lime,  and  30  cubic  feet  of  sand. 

The  San  Mateo  dam  in  California  was  not  built  up  as  a 
monolithic  mass  of  concrete  as  were  those  just  described,  but 
is  composed  of  great  concrete  blocks  of  uniformly  irregular 
dimensions.  These  blocks  (PL  XXIII)  weigh  9  tons  each,  and 
were  built  up  in  the  body  of  the  dam  in  such  manner  as  to  key 
in  with  each  other  both  in  horizontal  and  vertical  plan,  so  as  to 
produce  a  nearly  homogeneous  mass  and  create  the  greatest 
amount  of  friction  between  blocks.  The  material  was  mixed 
at  the  site  of  the  dam,  and  run  out  in  a  tramway  and  built  in 
place  inside  of  a  wooden  boxing  which  was  afterwards  re- 


2/O  MASONRY  DAMS, 

moved.  The  blocks  were  left  surrounded  by  the  boxing  for 
one  week,  during  which  time  they  set  sufficiently  for  the  wood 
to  be  removed  and  to  permit  of  other  blocks  being  built 
against  them.  The  concrete  consists  of  2-inch-gauge  metal 
mixed  in  the  proportion  of  6  of  broken  stone  to  2  of  sand  and 
i  of  Portland  cement. 

In  mixing  concrete  one  of  the  best  proportions  to  use, 
measured  by  volume,  is  I  part  of  cement,  2  of  clean  sharp  sand, 
and  3  to  4  of  broken  stone.  This  concrete  should  be  laid  im- 
mediately after  mixing,  and  should  be  thoroughly  rammed  and 
compacted  until  the  water  flushes  to  the  surface.  It  should  be 
allowed  to  stay  for  12  hours  or  more  before  any  further  work 
is  laid  upon  it. 

260.  Rubble  Masonry. — Rough  random  rubble  masonry 
is  considered  the  best  material  that  can  be  used  for  building 
a  dam.  It  possesses  strength,  can  be  readily  adapted  to  any 
form  of  profile,  and  is  relatively  cheap.  In  building  a  dam 
the  main  object  is  to  form  as  nearly  homogeneous  a  monolithic 
mass  as  possible.  Horizontal  and  vertical  courses  must  there- 
fore be  avoided,  and  the  stones  interlocked  in  all  directions. 
The  sizes  of  these  stones  may  differ  greatly.  The  mass  of  the 
wall  may  be  composed  of  stones  of  such  a  size  as  may  be  car- 
ried between  two  men,  as  is  the  case  in  India,  where  machinery 
is  rarely  employed ;  or  it  may  consist  of  cyclopean  rubble 
measuring  from  one  to  several  cubic  yards  in  volume,  each 
block  perhaps  weighing  several  tons.  To  prevent  leakage,  all 
spaces  between  the  stones  must  be  completely  and  compactly 
filled  with  impervious  mortar  or  cement.  To  prevent  sliding, 
the  blocks  must  be  irregularly  bedded,  and  as  each  course  is 
laid  a  large  proportion  of  the  stones  must  be  permitted  to  pro- 
ject above  the  general  surface.  The  spaces  between  the  larger 
stones  may  be  filled  with  concrete  or  small  rubble.  Grouting 
must  never  be  permitted,  and  the  best  stones  are  generally 
reserved  for  the  facing,  in  which  they  are  laid  as  headers 
in  such  manner  as  to  give  an  even  contour  to  the  outer 
surface. 


CEMENT— DETAILS  OF  CONSTRUCTION.  2J\ 

261.  Cement. — The  center  of  a  large  work  may  be  of  some 
cheaper  variety  of  cement,  as  Rosendale  or  other  natural  or 
American  cement.     Portland  cement  should   be  used  in   the 
facing  stones  and  in  pointing.     All   cement   used   should   be 
hydraulic  and  of  some  well-known  brand,  whether  natural  or 
Portland.     The  cement  should  be  carefully  enclosed  in  a  tight 
shed  with  a  close  floor  set  above  the  ground  to  protect  it  against 
dampness,  and   should  be  subjected  to  strict  inspection  and 
tests.     All  mortar  used  should  be  prepared  from  the  best  qual- 
ity of  cement  of  the  kind  above  described,  and  of  clean  sharp 
river  sand  well  washed  and  free  from  dirt.     They  should  be 
mixed  dry. in  the  proper  proportions,  and  then  a    moderate 
amount  of  water  should  be  added  and  the  whole  thoroughly 
worked  together.     Portland  cement  and  mortar  should   gen- 
erally be  mixed  in  the  proportion  of  about  I  of  cement  to  2  of 
sand  in  laying  the  puddle  work ;  while  for  laying  the  rubble 
work  and  concrete  I  of  cement  to  3  of  sand  may  be  used.     In 
laying  masonry  great  care  should  be  taken  that  water  shall  not 
interfere,  and  in  no  case  should  it  be  laid  in  water.     No  masonry 
should  be  built  in  the  winter  time  during  freezing  weather,  un- 
less exceptional  precautions  be  taken  to  cover  it  and  protect 
it  from  frost. 

262.  Details  of  Construction. — Rubble    stone    masonry 
should  always  be  made  of  sound  clean  stone,  of  suitable  size, 
quality  and    shape  for    the  work.     All    awkward    projections 
should    be   hammered  off   so   that   the   stones   shall   become 
rectangular  in   form.     Their  beds   should  present   such  even 
surfaces  that  when  the  stones  are  lowered  on  the  surface  pre- 
pared to  receive  them  there  can  be  no  doubt  that  the  mortar 
will  fill  all  spaces.     The  stones  should  be  well  rammed  into  the 
bed  of  mortar  if  they  are  light,  and  this  should  be  at  least 
one    inch    in    thickness.     Where   large    stones    are    employed 
a  moderate  quantity  of  spawls  may  be  used  in  the  prepara- 
tion of   suitable  surfaces  for  receiving  them.     Especial   care 
must  be  taken    to  have  beds  and   joints  full  of  water,  as  no 
grouting  or  filling  of  joints  should  be  allowed  after  the  stones 
are    placed.     The  work  must    be  thoroughly  bonded,  and   if 


2/2  MASONRY  DAMS. 

mortar  joints  are  not  full  and  flush  they  should  be  taken  oivt 
to  a  depth  of  several  inches  and  properly  repointed.  In  such 
work  various  sizes  of  stones  should  be  employed,  and  regular 
coursing  should  be  avoided  in  order  to  obtain  both  vertical 
and  horizontal  bonding.  The  sizes  of  the  stones  may  vary  with 
the  character  of  the  quarry,  but  where  the  thickness  of  the 
masonry  is  great  a  considerable  proportion  of  large  stones 
should  be  used.  Where  exceptionally  large  stones  are  em- 
ployed the  joints  may  be  filled  with  concrete  instead  of  mortar. 
In  such  cases  only  so  much  water  should  be  employed  as  can 
be  brought  to  the  surface  by  ramming. 

In  carrying  out  the  construction  of  rubble-masonry  work  it 
should  not  be  built  in  horizontal  courses ;  at  the  same  time  it 
must  be  built  in  beds,  and  these  should  be  irregularly  stepped, 
and  various  parts  of  the  structure  worked  upon  and  allowed  to 
set  at  different  times.  The  surface  of  these  horizontal  steps  or 
courses  should  bristle  with  projecting  stones,  so  as  to  secure  a 
perfect  bond  in  every  direction.  This  is  done  by  working  up 
the  mortar  or  concrete  between  the  stones  to  about  half  their 
height,  and  wherever  the  work  is  stopped  over  night  or  for  a 
period  of  time  these  projections  insure  bond  with  the  next 
layer  to  be  worked.  No  stones  should  be  deposited  or  dressed 
upon  the  wall,  but  on  platforms  or  planking,  so  that  no  dirt 
shall  be  brought  in  contact  with  the  material.  The  same  pre- 
caution must  be  taken  in  handling  concrete  and  mortar. 

The  rubble  facing  stones  should  be  of  large  size,  not  less 
than  2  feet  deep,  with  frequent  headers.  Where  especial  jar  is 
brought  on  the  masonry  work,  as  in  overfall  weirs,  facing  stones 
should  be  of  range  rubble,  of  the  soundest  and  most  durable 
quality,  and  should  be  cut  so  true  that  joints  not  exceeding  £ 
inch  shall  be  necessary  for  3  inches  from  the  surface,  the  remain- 
der of  the  joint  not  exceeding  2  inches  in  thickness  at  any  point. 
In  such  work  it  is  well  to  alternate  about  two  stretchers  for  one 
header,  and  to  make  the  former  not  less  than  3  feet  in  length, 
while  the  header  should  not  have  less  than  12  inches  lap  under 
ordinary  circumstances. 

The  concrete  used  in  work  of  this  character  should  be  made 


SUBMERGED   DAMS. 


273 


of  rough  broken  stone  metal,  and  of  clean  river  gravel  not  ex- 
ceeding from  2  to  2j-  inches  gauge.  This  material  should  be 
washed  free  of  dirt  before  being  used,  and  be  mixed  in  boxes, 
or  mortar  mixers  with  mortar  of  a  proper  quality.  The  pro- 
portions used  in  mixing  differ  greatly,  and  are  described  in 
technical  books  treating  on  this  subject. 

263.  Submerged  Dams. — In  a  few  instances  submerged 
dams  have  been  constructed  for  the  purpose  of  stopping  the 
underground  or  underflow  water  in  the  beds  of  streams.  This 


FIG.  76. — VIEW  OF  SAN  FERNANDO  SUBMERGED  DAM. 

has  been  resorted  to  particularly  in  a  few  streams  in  the  moun- 
tains of  Colorado  and  California,  where  the  surface  flow  is  large, 
but  as  the  streams  reach  the  plains  the  water  sinks  and  disap- 
pears. Its  downward  course  then  is  stopped  by  some  imper- 
vious bed  of  clay  or  rock,  and  there  is  created  practically  a  slow- 
moving  river  under  a  bed  of  deep  gravel.  This  can  be  brought 
to  the  surface  by  sinking  a  dam  entirely  across  the  stream  bed 
to  the  impervious  substratum,  when  the  water  will  be  raised, 
forming  an  underground  reservoir ;  or  a  series  of  cribs  may  be 


2/4  MASONRY  DAMS. 

built  on  the  impervious  stratum  under  the  gravels,  and  these 
will  catch  the  water  and  lead  it  off,  whence  it  may  be  removed 
by  an  open  cut  or  by  pumping  (Art.  295). 

The  former  method  is  employed  on  the  San  Fernando  Land 
and  Water  Company's  property  on  Pacoima  creek  in  Califor- 
nia. At  the  site  of  the  dam  the  canyon  walls  are  about  800 
feet  apart  and  the  bed-rock  about  75  feet  below  the  gravel 
surface  of  the  stream.  Through  this  a  trench  was  excavated, 
and  in  this  a  masonry  wall  was  built  up,  its  bed  width  being 
about  3  feet  and  its  top  width  2  feet,  its  greatest  depth  being 
53  feet  and  rising  to  a  height  of  from  2  to  3  feet  above  the 
stream  bed  (Fig.  76).  On  the  line  of  this  wall  are  two  large 
Wells,  and  on  its  upper  face  pipes  are  laid  in  open  sections,  so 
that  the  seepage  water  caught  by  the  dam  might  enter  these 
and  be  led  through  them  into  the  wells,  from  which  it  is  drawn 
off  for  purposes  of  irrigation. 

264.  Construction  in  Flowing  Streams. — In  building  any 
variety  of  dam  across  a  flowing  stream  the  expense  of  con- 
struction is  considerably  increased  by  the  necessity  of  hand- 
ling the  flowing  water  and  keeping  it  away  from  the  work  of 
construction.  Several  methods  are  pursued,  depending  largely 
upon  the  discharge  of  the  stream.  If  this  is  small,  one  of  the 
simplest  methods  is  to  build  an  under  or  scouring  sluice  in 
the  dam  and  construct  this  portion  of  the  work  first,  so  that 
the  water  may  be  permitted  to  flow  off  through  it  Avhile  the 
remainder  of  the  work  is  being  built.  If  the  stream  is  subject 
to  violent  floods  or  its  discharge  is  too  large  to  be  conveniently 
handled  in  this  manner,  wasteways  at  varying  heights  may  be 
left  in  the  crest  of  the  dam  over  which  the  floods  may  fall.  It 
is  frequently  necessary  to  build  a  temporary  dam  above  the 
main  structure  with  a  view  to  retaining  the  water  until  the 
latter  is  completed  ;  or  a  temporary  channel  may  be  built  for 
the  stream  around  the  dam,  and  through  this  the  water  may 
be  carried  off.  In  the  great  Tansa  and  Bhatgur  dams  in  India, 
where  the  floods  discharged  are  very  large,  a  portion  of  the 
masonry  adjacent  to  either  abutment  was  maintained  at  a 


SPECIFICATIONS  AND   CONTRACTS.  2?$ 

lower  height  than  the  rest  in  order  that  the  floods  might  flow 
over  it  as  over  a  wasteway. 

In  commencing  the  construction  of  a  dam  where  flowing 
water  has  to  be  controlled,  if  the  discharge  is  not  too  great 
the  stream  may  be  diverted  temporarily  while  the  main  por- 
tion of  the  dam  is  being  built ;  or  if  undersluices  are  to  be 
provided  for  the  discharge  of  the  water,  these  should  be  built 
first,  the  stream  being  passed  to  one  side  during  their  con- 
struction, after  which  it  may  be  turned  back  through  them, 
and  the  remainder  of  the  structure  carried  up.  If  no  under- 
sluices are  to  be  constructed,  pumping  may  be  resorted  to  if  a 
temporary  channel  cannot  be  provided,  though  this  method  is 
not  advisable  and  should  rarely  be  resorted  to.  In  founding 
a  dam  in  quicksand  two  or  three  methods  may  be  employed. 
Pneumatic  caissons  may  be  sunk,  and  the  foundation  built  in 
these  as  would  be  done  for  a  bridge  pier ;  or  if  the  sand  is 
comparatively  dry  and  semi-fluid,  it  may  be  frozen  by  the 
Poetsch  process,  and  the  excavation  for  the  foundation  can 
then  be  made  within  the  frozen  walls. 

265.  Specifications  and  Contracts. — There  are  many 
trivial  details  of  construction  which  must  be  considered  by  the 
engineer  in  designing  earth,  crib,  and  masonry  dams.  It  is 
customary  to  have  such  structures  built  by  contract,  and  for 
this  purpose  careful  specifications  are  drawn  up  by  the  en- 
gineer, detailing  the  character  of  material  and  construction. 
For  those  who  are  unfamiliar  with  such  forms  of  specifications, 
such  books  on  the  subject  of  specifications  and  contracts  as 
those  of  Gould  and  Haupt  can  be  purchased  ;  or  specifications 
which  have  been  used  by  other  engineers  can  be  obtained 
through  them. 

The  usual  form  of  specification  opens  with  a  general  de- 
scription of  the  work  and  its  location,  a  statement  of  the 
methods  and  appliances  to"be  used  in  construction,  a  descrip- 
tion of  the  protective  work,  highways,  bridges,  and  diverting 
works,  as  well  as  pumping  plant  and  other  temporary  work  to 
be  employed  during  construction.  For  earth  dams  the  speci- 
fications then  go  into  a  description  of  the  soil  to  be  used,  and 


2/6  MASONRY  DAMS. 

where  it  is  to  be  obtained ;  the  depth  of  excavation  and  its 
character,  and  the  method  of  retaining  it ;  a  description  of  the 
refilling  of  excavations  and  the  building  of  embankments  ; 
and  the  question  of  sodding  and  paving  or  revetting  the  em- 
bankments. 

If  the  dam  is  to  be  of  timber  or  loose  rock,  a  description  of 
the  timberwork  and  cribwork  is  given,  and  the  character  of 
the  rock  excavation  and  explosives  to  be  employed  is  entered 
into.  If  of  masonry,  the  matter  of  excavation  for  foundation, 
measurement  and  disposal  of  the  material  removed,  and 
method  of  stepping  the  foundation  are  first  considered.  Then 
the  hydraulic  masonry  is  described,  the  cement  and  its  tests, 
the  proportions  used  in  mixing  mortar  and  concrete,  the  char- 
acter of  the  brickwork  and  of  the  stone  masonry,  whether  of 
dry  rubble,  rubble  masonry,  range-rubble  facing,  or  cut-stone. 
In  addition  to  these  there  is  usually  some  iron  work  connected 
with  the  superstructure  and  gate-houses. 

266.  Examples   of  Masonry   Dams. — In   Table    XI    on 
page  222  were  given  the  general  dimensions  of  several  of  the 
largest   masonry  dams  which  have  been  built.     An  account  of 
the  construction  of  masonry  dams  would  be  incomplete  with- 
out  a  few  examples  of  the  larger  and    more  typical  of  the 
modern  dams,  and  accordingly  brief  descriptions  and  illustra- 
tions of  some  of  these  are  given  here.     These  are  divided  for 
convenience  into  two  general  classes :   I,  those  which  act  as  re- 
taining walls  for  the  water  and  over  which  the  latter  is  not  ex- 
pected to  flow ;  and  2,  those  which  act  both  as  retaining  walls 
and  overflow  weirs.     The  older  and  less  typical  forms  of  dams, 
such  as  those  built  in  Spain  in  earlier  days,  and  a  few  of  those 
built  in  France  and  elsewhere,  do  not  require  description  here, 
as  no  such  works  are  likely  to  be  designed  in  the  future.     For 
those  who  are  interested  in  their  study,  descriptions  and  cross- 
sections  of  these  can  be  found  either  in  Wegmann's  "Design 
and    Construction  of    Masonry  Dams,"    Krantz's   "  Reservoir 
Walls,"  or  in  the  I2th  and  I3th  Annual  Reports  of  the  U.  S. 
Geological  Survey. 

267.  Furens   Dam,    France. — This  is  one  of  the  largest 


FURENS  DAM,    FRANCE, 


277 


and  first  of  the  great  dams  built  according  to  modern  formu- 
las (Fig.  77).  It  is  170.6  feet  in  maximum  height  above  bed- 
rock, the  maximum  depth  of  water  being  164  feet ;  its  thick- 
ness at  top  9.9  feet,  and  at  the  base  161  feet.  The  maximum 
pressure  on  the  masonry  is  6.82  tons  per  square  foot  while  its 


45.9 


4908 
FIG.  77. — CROSS-SECTION  OF  FURENS  DAM,  FRANCE. 

total  length  is  328  feet  on  top.  In  plan  it  is  curved  with  a 
radius  of  828.4  feet,  and  it  is  built  entirely  of  rubble  masonry, 
the  facings  being  of  the  same  material.  The  top  of  the  dam 
is  finished  off  as  a  roadway  9.8  feet  wide,  and  this  is  protected 
by  two  parapets,  one  on  either  side,  each  1.6  feet  in  height. 


278 


MASONRY  DAMS. 


268.  Gran  Cheurfas  Dam,  Algiers.— This  dam  (Fig.  78) 
was  built  in  1882,  and  has  a  total  height  above  its  foundation 
of  98.4  feet.  Its  width  at  top  is  13.1  feet,  at  the  base  72.2  feet, 
and  its  top  length  is  508.4  feet.  It  is  built  practically  in  two 
parts,  the  first  consisting  of  a  trapezoidal-shaped  foundation 


4.00 


FIG.  78. — CROSS-SECTION  OF  GRAN  CHEURFAS  DAM,  ALGIERS. 

mass  of  rubble,  on  which  is  built  the  dam,  the  upper  and  lower 
surfaces  of  which  are  parabolic.  The  depth  of  water  which 
this  dam  will  hold  is  132.2  feet,  and  the  maximum  pressure  on 
the  masonry  within  it  is  6.14  tons  per  square  foot.  In  plan  it 
is  straight. 


TANSA    DAM,  INDIA. 


279 


269.  Tansa  Dam,  India. — This  great  dam  is  built  through- 
out of  uncoursed  rubble  masonry.  It  is  designed  to  have  a 
total  height  of  133  feet,  though  it  has  as  yet  been  completed 
only  to  a  height  of  118  feet  (Fig.  79).  At  this  height  its 
maximum  top  width  is  15.2  feet,  while  its  maximum  width  at 


*</»'     rieod  Ltr*/ 


Ntf*.^    fr»Sivru  rttvrur  vnffy.jn  /&>,/*/•  fp.   /acA 

FIG.  79.— CROSS-SECTION  OF  TANSA  DAM,  INDIA. 

base  is  96.5  feet.  Its  total  length  on  top  is  9350  feet,  while  in 
plan  it  is  built  in  two  tangents,  the  apex  pointing  up-stream. 
Near  the  south  end  is  built  a  wasteway  1800  feet  in  length, 
its  crest  being  3  feet  below  that  of  the  dam.  This  wasteway 
is  built  in  a  portion  of  the  dam  where  its  height  is  but  a  few 
feet,  and  it  discharges  back  directly  into  the  river  channel 
below  the  toe  of  the  structure.  Near  the  base  of  the  dam 


BHATGUR  DAM,   INDIA. 


281 


is  a  large    outlet   tunnel,  which  discharges   into   the   conduit 
which  carries  the  water  to  Bombay  for  the  supply  of  that  city. 


FIG.  80. — CROSS-SKCTION  OF  BHATGUR  DAM,  INDIA. 

270.  Bhatgur  Dam,  India.— This  dam  (PI.   XXII)  is  4067 
feet  in  length,  and  is  constructed  throughout  of  the  best  un- 


282  MASONRY  DAMS. 

coursed  rubble  masonry  in  cement.  On  the  faces  the  dressed 
rubble  is  laid  up.  in  courses.  It  is  127  feet  in  height,  74  feet  in 
width  at  the  base,  and  12  feet  wide  on  top  (Fig.  80).  When 
full  the  pressure  on  the  lower  toe  is  5.8  tons  per  square  foot, 
and  when  empty  the  pressure  at  the  upper  toe  is  6.7  tons  per 
square  foot.  In  plan  the  dam  curves  irregularly  across  the 
valley,  following  an  outcrop  of  rock.  Portions  of  either  end 
of  the  dam,  where  it  is  not  high,  are  left  8  feet  lower  than  the 
remainder  so  as  to  act  as  wasteways.  The  total  length  of 
these  wasteways  is  810  feet,  and  they  are  arched  over  in  such 
manner  as  to  leave  a  roadway  across  their  tops.  Below  the 
dam  and  jutting  from  it  are  masonry  walls  which  lead  the 
waste  water  off  in  such  manner  that  it  flows  clear  of  the  foot 
of  the  dam  and  passes  off  through  separate  channels  to  the 
main  stream  below.  For  the  purpose  of  scouring  silt  which 
may  be  deposited  in  the  reservoir,  fifteen  undersluices  are 
constructed  near  the  centre  of  the  dam,  at  its  deepest  part. 
These  are  placed  17  feet  apart  and  are  4  by  8  feet  in  dimen- 
sions, their  sills  being  60  feet  below  high-water  mark.  Above 
these  are  two  other  undersluices  for  discharging  the  water  to 
be  used  in  irrigation  when  the  reservoir  is  full.  One  of  these 
is  20  feet  and  the  other  50  feet  above  the  main  row  of  under- 
sluices. 

271.  New  Croton  Dam,  New  York. — This  monster  dam 
will  be  of  composite  construction.  For  about  530  feet  from  the 
left  bank  it  will  be  of  earth.  The  next  630  feet  of  its  length 
will  consist  of  a  high  masonry  dam  designed  on  a  theoretic 
profile.  Thence  to  the  left  bank  the  structure  will  consist  of 
a  masonry  overfall  weir  of  heavy  cross-section  and  1020  feet  in 
length  on  the  crest.  The  capacity  of  the  reservoir  will  be 
92,000  acre-feet. 

The  earth  dam  will  be  245  feet  in  extreme  height  above  its 
foundation  and  120  feet  above  the  ground  surface  (Fig.  81). 
Its  top  width  will  be  30  feet  and  will  be  20  feet  above  high- 
water.  Through  its  centre  will  be  built  upon  a  rock  foun- 
dation a  masonry  core-wall  18  feet  wide  at  the  base  and 
sloping  on  both  faces  to  a  top  width  of  6  feet  at  a  level  with 


NEW  CROTON  DAM,   NEW   YORK. 


283 


high-water.  The  upper  or  water  face  will  have  a  slope  of  i 
on  2,  and  will  be  paved  with  from  if  to  2  feet  of  cobbles  laid 
on  I  to  I J  feet  of  broken  stone.  The  lower  slope  will  be  I  on 


FIG.  81.— CROSS-SECTION  OF  EARTH  EMBANKMKNT.    NEW  CROTON  DAM,  CORNELL'S. 

2,  and  will  be  broken  by  three  benches. each  5  feet  wide  and 
paved  to  make  a  gutter  to  catch  drainage.  This  slope  will  be 
carefully  sodded. 

The  main  dam  will  be  connected  with  the  earth  dam  by 
heavy  masonry  wing  walls  and  the  masonry  core  wall.  It  will 
have  an  extreme  height  of  248  feet  above  its  foundation  and 
will  be  163  feet  in  height  above  the  river  bed.  The  high- 
water  level  or  crest  of  the  overfall  weir  will  be  14  feet  below 
the  crest  of  the  dam.  Its  extreme  width  at  base  will  be  185 
feet  and  at  its  top  18  feet,  surmounted  by  a  4-foot  coping.  This 
structure  will  be  built  throughout  of  the  best  rubble-stone 
masonry,  faced  above  the  ground  surface  with  coursed  stones 
set  in  Portland  cement. 

In  plan  the  earth  and  masonry  section  will  be  straight  to 
the  masonry  overfall  weir,  which  will  curve  up-stream  nearly 
at  right  angles  to  the  main  structure.  The  water  falling  over 
this  weir  will  spill  into  an  artificial  channel  excavated  in  the 
hillside  and  emptying  into  the  main  channel  below  the  toe  of 
the  dam.  The  extreme  height  of  the  weir  will  be  150  feet  and 
its  extreme  width  at  base  195  feet.  It  will  have  a  very  slight 


284 


MASONRY  DAMS. 


TlG.  82.— CROSS-SECTION  OF  MASONRY  DAM.    NEW  CROTON  DAM.  CORNELLS. 


|^-i-£.   CL^rf^^.-z ^ 

FIG.  83.— CROSS-SECTION  OF  OVERFALL  WEIR.     NEW  CROTON  DAM,  CORNELL'S. 


PERIAR  DAM,   INDIA. 


285 


batter  on  the  up-stream  side,  while  its  lower  side  will  have  a 
slightly  ogee-shaped  curve  and  will  be  broken  by  25  steps 
varying  from  2  to  10  feet  in  height.  This  weir  will  be  con- 
structed, like  the  dam,  of  an  uncoursed  rubble  masonry  interior 
and  coursed  faces. 


FIG.  84. — CROSS-SECTIONS  OF  PKRIAR  DAM  AND  WASTH  WEIR,  INDIA. 

272.  Periar  Dam,  India. — This  dam,  which  is  constructed 
throughout  of  concrete,  is  1230  feet  long  on  top.  It  has  a  maxi- 
mum height  (Fig.  84)  of  173  feet  (the  numbers  on  the  illustra- 
tion being  incorrect  as  they  were  taken  from  a  preliminary 


286 


MASONRY  DAMS. 


BEETALOO   AND    SAN  MATEO   DAMS 


287 


design  for  the  dam).  Its  crest  is  surmounted  by  a  parapet  $ 
feet  in  height,  the  maximum  depth  of  water  which  the  dam  will 
hold  being  160  feet,  and  its  width  at  base  138  feet  9  inches,  its 
top  width  being  12  feet.  At  either  end  are  two  wasteways  built 
in  solid  rock,  forming  the  abutments  of  the  dam  and  separated 
from  it,  their  aggregate  length  being  920  feet.  The  maximum 
capacity  of  the  reservoir  will  be  306,000  acre-feet,  its  available 
capacity  being  157,000  acre-feet. 

273.  Beetaloo  Dam,  South  Australia. — This  structure 
(Fig.  85)  is  no  feet  in  maximum  height,  no  feet  wide  at  the 
base,  and  14  feet  wide  on  top.  Its  length  on  top  is  580  feet, 
and  it  is  curved  in  plan,  the  convex  side  facing  up-stream.  It  is 


FIG.  85.— CROSS-SUCTION  OF  BEETALOO  DAM,  AUSTRALIA. 

constructed  throughout  of  concrete,  and  in  one  end  of  the  dam  is 
built  a  set  of  three  wasteways,  their  total  length  being  200  feet 
with  their  crests  5  feet  below  that  of  the  main  structure.  These 
wasteways  are  separated  by  masonry  walls,  which  lead  the  flood 
waters  back  into  the  river  below  and  clear  of  the  structure. 

274.  San  Mateo  Dam,  California.— This  structure  is  built 
throughout  of  concrete,  not  as  a  monolithic  mass,  as  is  the 
case  with  the  Beetaloo  and  Periar  dams,  but  as  described  in 
Article  259,  it  was  built  up  in  blocks  set  in  place,  the  weight 
of  each  being  about  9  tons.  In  cross-section  this  structure  is 
heavier  than  theory  alone  would  require.  As  shown  in  PI. 
XXIII,  its  maximum  height  is  170  feet,  its  crest  being  5  feet 
above  high-water  mark,  at  which  level  is  a  wasteway  built  a 


288 


MASONXY  DAMS. 


SWEEl^WATER   DAM,    CALIFORNIA.  289 

short  distance  above  the  north  end  of  the  dam  and  separated 
from  it  by  a  low  ridge.  The  top  width  of  the  dam  is  25  feet 
and  its  width  at  the  bottom  is  176  feet.  Its  upper  slope  has  a 
uniform  batter  of  4  on  I,  while  the  lower  slope,  beginning  with 
a  batter  of  2^  on  I  at  the  top,  curves  to  within  a  few  feet  of 
the  bottom,  where  the  batter  becomes  I  on  I.  In  plan  this 
structure  is  curved  up-stream. 

275.  Sweetwater  Dam,  California.— This  dam  (PI.  XXVI) 
is  slighter  in  cross-section  than  theory  would  require,  and  de- 
pends to  a  certain  extent  on  its  curved  plan  for  its  stability.     As 
shown  in  Plates  XXIV  and  XXV,  it  is  90  feet  in  maximum 
height,  380  feet  long,  12   feet  wide  on  top  and  46  feet  wide  at 
the  base.     The  radius  of  its  curvature  is  222  feet,  and  as  the 
length  of  the  radius  is  small  and  the  curvature  great,  this  adds 
considerably  to  its  stability.    The  structure  is  built  throughout 
of  large   uncoursed  rubble  masonry,  the  greatest  care  having 
been  used  in  every  detail  of  construction.     At  its  southern  end 
are  a  set  of  seven  escape-ways  40  feet  in  aggregate  width,  so 
arranged  that  the  water  issuing  through  them  drops  first  into 
a  series  of  water  cushions,  and  is  then  led  off  by  a  directing 
wall  so  as  to  clear  the  dam.     Near  its  base  is  a  discharge  sluice, 
operated  from  a  water  tower  in  the  reservoir. 

276.  Vyrnwy  Dam,  Wales. — This  structure  is  peculiar  in 
cross-section  (Fig.  86),  being  unusually  heavy,  and  much  greater 
than  theory  would  demand.     The  reason  for  this  is  that  the 
crest  of   the   whole   dam    acts  as  a  waste  weir,  which  is  sur- 
mounted  by  arches   on  which   rests  a  roadway,  and  beneath 
these  arches  the  waste  waters  are  permitted  to  flow.     Its  lower 
face  is  given  an  ogee-shaped  curve  so  as  to  reduce  to  a  mini- 
mum the  shock  of  the  falling  water,  and  there  is  a  depth  of  45 
feet  of  back-water  on  its  toe,  which  forms  a  sort  of  water  cushion. 
Its  maximum  height  is   136  feet,  while  the  greatest  depth  of 
water  is  129  feet.     Its  width  at  base  is  1 17.7  feet,  and  the  upper 
curved  portion   rests  on  a  massive  pedestal  nearly  rectangu- 
lar in  cross-section  and  43  feet  in  height.     This  dam  is  straight 
in  plan,  its  total  length  on  top  being   1350  feet,  and  it  is  built 


2QO 


MASONRY  DAMS. 


VYRNWY  DAM,    WALES. 

throughout  of  large  cyclopean  rubble,  the  stones  weighing  from. 
2  to  8  tons  apiece. 


FIG.  86.  —CROSS  SECTION  OF  VYRNWY  DAM,  WALES. 

277.  Betwa  Dam,  India. — This  structure,  which  has  an- 
unusually  heavy  cross-section  (Fig.  87),  performs  the  functions 
of  a  weir,  the  flood  waters  passing  over  the  entire  crest  to  an 
extreme  depth  of  6£  feet.  In  plan  it  is  built  in  three  tangents, 
following  the  line  of  an  outcrop  of  rock.  Its  total  length  is, 
3296  feet,  its  top  width  being  15.2  feet,  and  its  maximum 
height  about  64  feet.  The  down-stream  face  of  this  weir  is. 
supported  by  a  buttress  or  block  of  masonry  15  feet  in  width 


I 


BE  7 'W 'A    DAM,    INDIA. 


293 


and  20  feet  in  height,  while  above  it  the  back-water  in  the  river 
rises  to  an  additional  height  of  about  10  feet,  so  that  the  flood 
waters  will  fall  on  a  water  cushion  of  this  depth  and  then  on 
the  solid  buttress.  This  structure  is  built  throughout  of  un- 
coursed  rubble  masonry,  its  faces,  however,  being  coursed  with 
dimension  stone  and  the  coping  being  of  ashlar.  In  the  river 
some  distance  below  its  highest  portion  is  built  a  subsidiary 


FIG.  87.— CROSS-SECTION  OF  BETWA  DAM,  INDIA. 

or  smaller  weir,  which  backs  the  water  up  against  the  toe  of 
the  main  weir  in  such  manner  as  to  form  the  water-cushion  on 
which  the  floods  may  fall.  The  extreme  height  of  this  sub- 
sidiary weir  is  1 8  feet,  and  the  height  of  overfall  from  the 
main  weir  to  the  surface  of  the  water  cushion  is  2\\  feet, 
though  in  time  of  greatest  flood  this  will  be  reduced  to  8  feet. 
The  top  width  of  the  subsidiary  weir  is  12  feet,  and  its  walls 
are  nearly  vertical  on  the  down-stream  side,  with  a  slope  of 
10  to  I  on  the  up-stream  side. 


TURLOCK  AJVD  FOLSOM  DAMS. 


295 


278.  Turlock  Dam,  California.— This  structure  (Fig.  88) 
is  a  little  heavier  in  cross-section  than  theory  alone  would 
demand,  as  it  is  expected  that  the  flood  waters  of  the  Tuo- 
lumne  river  will  pass  over  its  entire  crest  to  a  possible  maxi- 
mum depth  of  1 6  feet.  About  200  feet  below  the  main  dam 
is  built  a  subsidiary  weir  20  feet  in  height  and  120  feet  in 
length,  its  top  width  being  12  feet.  This  weir  will  back  the 
water  up  against  the  toe  of  the  main  weir  to  a  depth  of  15 


FIG.  88. — CROSS-SECTION  OF  TURLOCK  DAM. 

feet,  thus  giving  a  water  cushion  on  which  the  floods  may  fall. 
The  main  weir  is  straight  in  plan,  310  feet  in  length  on  top, 
96  feet  in  width  at  the  base,  20  in  width  on  top,  and  130 
feet  in  maximum  height,  and  is  built  throughout  of  uncoursed 
rubble  masonry.  There  is  no  escape-way,  while  there  are  a 
couple  of  undersluices  which  served  to  pass  water  during  con- 
struction. 

279.  Folsom  Dam,  California. — This  structure  (PL 
XXVII),  like  that  just  described,  acts  only  as  a  diversion  weir. 
It  is  69^  feet  in  maximum  height  on  the  up-stream  side,  and 
98  feet  in  height  on  the  down-stream  side.  Its  cross-section  is 
unusually  heavy,  as  flood  waters  to  a  depth  of  over  30  feet  are 
expected  to  flow  over  its  crest  (PL  XXVIII).  Its  top  width  is 
24  feet  and  its  extreme  width  at  base  87  feet,  the  toe  termi- 
nating in  a  heavy  buttress  of  masonry.  Its  total  length  on  the 
crest  is  about  520  feet,  a  large  portion  of  which  consists  of  a 
retaining  wall  leading  to  the  canal  entrance.  One  hundred 
and  eighty  feet  in  length  in  the  centre  of  the  main  dam  is 
lowered  a  depth  of  6  feet  to  form  a  wasteway  over  which  the 


MASONRY  DAMS. 


CROSS  SECTION  QF'WEIR 

PLATE  XXVIII. — FOI.SOM  CANAL,  PLAN  AND  CROSS-SECTION  OF  WEIR. 


COLORADO   RIVER  DAM,    TEXAS. 


297 


floods  jnay  pass,  and  this  wasteway  is  closed  by  a  single  long 
shutter,  consisting  of  a  Pratt  truss  backed  with  wood,  which 
can  be  raised  and  lowered  by  means  of  hydraulic  presses, 
operated  from  a  power-house  near  by.  The  dam  is  constructed 
throughout  of  uncoursed  rubble  masonry. 

280.  Colorado  River  Dam,  Texas. — This  dam  is  built 
.-.cross  the  Colorado  river  for  the  supply  of  water  and  water- 
power  to  the  city  of  Austin,  Texas.  Its  interior  is  of  rubble 
masonry,  faced  on  both  sides  and  on  top  with  large  cut  blocks 
of  coursed  granite.  It  is  1275  feet  long  on  top,  1125  feet  of 
which  are  constructed  as  an  overfall  wasteway,  and  66  feet  in 
maximum  height,  its  upper  face  being  vertical.  The  lower  face 
has  an  easy  ogee-shaped  curve  (Fig.  89),  calculated  to  pass  the 


FIG.  89.— CROSS-SECTION  OF  COLORADO  RIVER  DAM. 

waters  with  such  ease  that  the  erosive  action  at  the  base  will 
be  reduced  to  a  minimum.  The  structure  is  practically  a  great 
overfall  weir,  the  maximum  flood  to  be  passed  being  estimated 
at  250,000  second-feet  from  a  catchment  basin  of  50,000  square 
miles. 

The  cross-section  is  somewhat  heavier  than  theory  would 
demand  if  the  dam  were  built  to  act  as  a  retaining  wall  only. 
The  lower  portion  of  the  down-stream  face  is  curved  with  a 
radius  of  31  feet  tangent  at  the  bottom  to  low-water  surface, 
so  as  to  deliver  the  floods  away  from  the  toe  and  against  the 
back-water  in  the  river.  The  upper  end  of  the  curve  is  tangent 


298 


MASONRY  DAMS. 


to  the  main  slope,  which  has  a  batter  of  3  in  8,  and  ends  on 
top  in  a  curve  of  20  feet  radius.  This  top  curve  is  tangent  to 
the  horizontal  crest  line,  which  is  5  feet  wide.  The  total  top 
width  is  16  feet,  and  the  maximum  width  at  base  68  feet. 

281.   Bear  Valley  and  Zola  Dams. — The  most   notable 
curved  dams  are  the  Bear  Valley  dam  in  California,  and  the 


FIG.  90. — CROSS-SECTION  OF  BEAR  VALLEY  DAM. 

Zola  dam  in  France,  the  cross-sections  of  which  are  unusually 
light,  as  they  depend  chiefly  on  their  curved  plan  for  their 


FIG.  91.  —  PLAN  AND  ET.KVATION  OF  BEAR  VALLEY  DAM. 


stability.  The  former  (Fig.  90)  is  but  3.2  feet  in  width  on  top, 
and  at  a  depth  of  48  feet  below  its  crest  its  width  is  but  8.4 
feet.  At  this  point  an  offset  of  2  feet  is  made  on  each  side, 


BEAR    VALLEY  AND   ZOLA    DAMS. 


299 


and  its  width  thence  increases  to  20  feet  at  its  base,  which  is 
at  a  point  64  feet  below  its  crest.     This  structure  is  450  feet  in 


FIG.  92. — CROSS-SECTION  OF  ZOLA  DAM,  FKANCK. 

length  on  top,  and  in  plan  it  is  curved  with  a  3OO-foot  radius 
(Fig.  91).     It  is  built  throughout  of  the  best  uncoursed  rubble 


3OO  MASONRY  DAMS. 

granite  masonry,  and  depends  almost  wholly  on  its  curved  plan 
and  the  excellence  of  its  construction  for  its  stability,  since  the 
lines  of  pressure  with  the  reservoir  full  fall  from  13  to  15  feet 
outside  of  its  base. 

The  Zola  dam  (Fig.  92)  is  123  feet  in  maximum  height,  19 
feet  in  width  on  top,  and  41.8  feet  in  width  at  the  base.  Its 
length  on  top  is  205  feet,  and  it  is  curved  with  a  radius  of  158 
feet.  Like  the  Bear  Valley  dam,  it  depends  chiefly  on  its 
curvature  and  the  excellence  of  its  construction  for  its  stability. 
The  material  of  which  it  is  built  is  uncoursed  rubble  masonry. 

282.  Works  of  Reference.     Storage  Works. — 

BAKER,  IRA  O.    A  Treatise  on  Masonry  Construction.     John  Wiley  & 

Sons,  New  York,  1890. 
CHURCH,  IRVING  P.     Mechanics  of  Engineering.     Fluids.    John  Wiley 

&  Sons,  New  York,  1889. 
FANNING,  J.  T.     Hydraulic  and   Water-supply  Engineering.     D.   Van 

Nostrand  &  Co.,  New  York,  1890. 
FRANCIS,  J.  B.     High  Walls  or  Dams  to  resist  the  Pressure  of  Water. 

Trans.  Am.  Soc.  C.  E.,  New  York,  vol.  xix,  1888. 
GOULD,    B.   SHERMAN.    Contract    and    Specifications   for   Building  a 

Masonry  and  Earthen   Dam.     Engineering   News   Pub.  Co.,  New 

York. 
HALL,  WM.  HAM.     Irrigation  in  Southern  California.     Report  as  State 

Engineer  of  Cal.     Sacramento,  1888. 

JACOBS,  ARTHUR.    The  Designing  and  Construction  of  Storage  Reser- 
voirs.    D.  Van  Nostrand  &  Co.,  New  York,  1888. 
KRANTZ,  J.  B.    A  Study  on  Reservoir  Walls.    Translated  by  F.  Mahan. 

John  Wiley  &  Sons,  New  York,  1883. 
MERRIMAN,  MANSFIELD.     Text-book  on  Retaining  Walls  and  Masonry 

Dams.     John  Wiley  &  Sons,  New  York,  1892. 
MCMASTERS,  JOHN  B.     High  Masonry  Dams.     D.  Van  Nostrand  &  Co., 

New  York,  1876. 

RONNA,  A.  Les  Irrigations.  2  vols.  Firmin-Didot  et  Cie,  Paris,  1889. 
VISCHER,  HUBERT,  and  WAGONER,  LUTHER.  On  Strains  in  Curved 

Masonry  Dams.     Trans.  Tech.  Soc.  Pacific  Coast,  vol.  xi,  1890. 
WEGMANN,  EDWARD,  JR.     Design  and  Construction  of  Masonry  Dams. 

John  Wiley  &  Sons,  New  York,  1889. 
WEISBACH,  P.  J.,  and  Du  Bois,  A.  JAY.     Hydraulics   and   Hydraulic 

Motors.    John  Wiley  &  Sons,  New  York,  1889. 


CHAPTER   XX. 
WASTEWAYS   AND   OUTLET   SLUICES. 

283.  Wasteways. — Wasteways,  escapes,  or  spillways  as 
they  are  sometimes  called,  are  an  essential  adjunct  of  every 
dam.  They  are  to  a  reservoir  what  a  safety-valve  is  to  a  steam- 
engine  ;  the  means  of  disposing  of  surplus  waters  due  to  floods 
and  preventing  these  from  topping  the  dam  and  possibly  caus- 
ing its  destruction.  Water  should  not  be  permitted  to  flow 
over  the  crest  of  a  masonry  dam  unless  it  has  been  built  in  an 
unusually  substantial  manner  calculated  to  withstand  the  shock 
of  this  overfall.  It  should  never  be  permitted  to  flow  over  the 
face  of  a  loose-rock  or  earth  dam.  The  outer  slope  of  an  earth 
dam  is  its  weakest  part,  and  if  water  is  permitted  to  top  it  it 
will  speedily  cut  it  away  and  cause  a  breach. 

Too  many  of  the  great  floods  which  have  occurred  in  recent 
years  bear  testimony  to  the  necessity  of  constructing  substan- 
tial and  ample  wasteways.  Moreover,  an  ample  wasteway  being 
provided,  the  greatest  care  should  be  exercised  to  maintain  it 
always  open  and  ready  for  use,  independent  of  all  undersluices 
and  other  discharge  outlets  which  may  be  closed  by  valves  or 
other  mechanical  means.  To  the  lack  of  one  or  both  of  these 
precautions  was  due  the  destruction  of  the  South  Fork  dam  in 
Pennsylvania  in  1889;  of  the  Walnut  Grove  dam  in  Arizona  in 
the  spring  of  1890,  and  many  other  similar  catastrophes.  Had 
the  wasteway  of  the  South  Fork  dam  been  ample,  as  it  origi- 
nally was,  the  water  would  not  have  flowed  over  the  crest  of  the 
dam  and  have  caused  its  destruction.  But  the  wasteway  was 
barred  by  fish-screens,  and  these  not  only  obstructed  the  pas- 

301 


302  W 'A  S  TE  WA  YS  A ND    O  U  TLE  T  SL  UICES. 

sage  of  the  water  but  caught  floating  timber  and  logs  brought 
down  by  the  flood,  which  so  diminished  the  area  of  the  spill- 
way as  to  cause  the  waters  to  top  the  dam.  In  the  case  of  the 
Walnut  Grove  dam  the  area  of  the  wasteway  was  unquestion- 
ably insufficient,  resulting  consequently  in  the  passage  of  much 
of  the  flood  water  over  the  dam  crest  and  resulting  in  the 
destruction  of  the  work. 

284.  Character  and  Design  of  Wasteways. — In  design- 
ing a  wasteway  for  a  reservoir  data  relating  to  the  greatest 
floods  likely  to  occur  must  be  sought  for  in  its  catchment  basin, 
and  the  dimensions  of  the  wasteway  must  be  proportioned  for 
the  extraordinary  floods.     The   methods  of  determining  the 
great  floods  and  the  necessity  for  looking  for  signs  of  these  in 
the  valleys  has  already  been  discussed  in  Chapter  IV.    Should 
other  reservoirs  exist  above  that  under  consideration  provision 
should  be  made  for  the  discharge  of  their  contents  lest  their 
embankments  give  way;  this  can  only  be  done  by  considering 
their   volume   and    calculating   the   velocity   and    consequent 
quantity  which  will  reach  the  dam  at  any  one  time. 

Having  fixed  on  the  area  of  the  wasteway  from  a  knowledge 
of  the  maximum  flood  to  be  discharged,  the  chief  consideration 
to  be  borne  in  mind  is  the  relation  of  its  depth  to  its  length. 
A  long  wasteway  may  permit  the  loss  of  too  great  a  volume  of 
water  if  exposed  to  the  action  of  the  wind,  whereas  a  short  one 
renders  it  necessary  to  give  the  dam  an  increased  height  in 
order  that  it  may  have  the  required  capacity.  The  depth  of 
the  wasteway  will  be  largely  regulated  by  the  probable  wave- 
height,  and  this  will  depend  on  the  depth  and  fetch  of  the  res- 
ervoir (Article  237).  The  difference  in  height  between  the  crest 
of  the  dam  and  the  wasteway  will  generally  vary  between  3  and 
10  feet  as  limits.  Care  should  always  be  taken  in  designing  a 
wasteway  to  rapidly  increase  the  slope  of  its  bed  immediately 
below  the  crest  of  the  waste  weir,  so  that  there  shall  be  no 
piling  or  banking  up  of  water  to  retard  the  discharge.  A  quick 
drop  beyond  the  crest  considerably  enhances  the  discharging 
capacity. 

285.  Discharge  of  Waste  Weirs. — For  the  calculation  of 


DISCHARGE   OF    WASTE    WEIRS.  303 

discharge  the  wasteway  can  be  considered  as  a  measuring  weir 
subject  to  the  weir  formulas.  If  the  crest  of  the  wasteway  has 
a  sharp  square  edge  or  falls  away  with  considerable  suddenness 
on  the  lower  side,  Francis'  formula  (Art.  86)  may  be  applied 
with  approximate  results,  and  we  have 


......     (i) 

The  mean  velocity  of  flow  o'ver  the  crest  is 


and  multiplying  the  depth    of  water  on  the  weir   h  into  its 
length  /  we  get  the  volume  of  discharge. 

When  the  overfall  from  the  crest  is  not  sudden 


(2) 


in  which  m  is  a  coefficient  of  contraction  with  the  value  of 
about  .62.  Where  the  overfall  weir  has  a  wide  crest  the  follow- 
ing formula,  suggested  by  Mr.  Francis,  is  the  most  accurate  for 
depths  between  6  and  18  inches,  viz., 

0=3.012/7*  ''53  .........        (3) 

Another  formula  and  one  commonly  used  in  India  for  deter- 
mining the  discharge  of  wasteways  is 

Q  =  I  X  \c  X  8.02 


in  which  c  is  a  coefficient  which  varies  with  the  form  of  the 
weir  and  rarely  exceeds  .65,  though  with  a  majority  of  weirs  it 
is  about  equal  to  .62.  In  which  case 


where  d  is  the  maximum  depth  in  feet  of  water  to  be  permitted 
to  pass  over  the  weir.  Ordinarily  there  is  no  velocity  of  ap- 
proach to  a  reservoir  wasteway,  though  should  the  water  reach 
the  latter  by  a  cut  it  may  be  necessary  to  take  the  velocity  of 
approach  into  account. 


304  WASTEWAYS  AND   OUTLET  SLUICES. 

286.  Classes  of  Wasteways. — Wasteways  maybe  divided 
into  three  general  classes,  depending  upon  the  character  of  the 
dam  and  the  topography  of  the  site.  First,  the  entire  struc- 
ture, if  of  masonry,  may  be  utilized  as  a  wasteway.  This  can 
only  be  done  by  making  the  cross-section  of  the  dam  unusually 
heavy  and  providing  it  against  the  shock  of  falling  water  as  in 
the  case  of  the  Folsom,  Turlock,  Betwa,  Colorado  River,  and 
Vyrnwy  dams  (Articles  276  to  280).  Second,  if  the  dam  is  of 
masonry  it  may  be  given  the  theoretical  cross-section  and  the 
wasteway  made  in  one  end  of  it,  if  the  dam  at  this  point  is 
sufficiently  low  not  to  subject  it  to  great  shock  from  the  falling 
water.  This  is  the  case  with  the  Bhatgur,  Tansa,  and  New 
Croton  dams  (Articles  269  to  271). 

It  is  never  advisable  to  build  a  wasteway  in  earth  or  loose- 
rock  dams,  as  it  is  difficult  to  make  a  safe  bond  between  the 
masonry  wasteway  and  the  earth  dam,  and  unless  extraordi- 
nary circumstances  demand  it  such  an  arrangement  should  be 
avoided.  In  some  cases,  however,  this  has  been  done,  great 
care  being  taken  in  connecting  the  two  classes  of  work  and  the 
wasteway  being  carefully  lined  with  masonry  and  provided 
with  masonry  wing  walls  for  the  protection  of  the  earth  em- 
bankment. 

The  third  general  class  of  wasteways  is  where  these  are 
built  in  the  hillsides  at  some  distance  from  the  dam.  If  on 
the  slopes  adjacent  to  one  end  of  the  dam,  the  discharge  water 
must  be  so  directed  by  retaining  walls  that  it  will  flow  back 
into  the  stream  channel  clear  of  the  toe  of  the  dam.  Such 
wasteways  may  be  excavated  in  the  solid  rock,  or  if  in  earth 
they  should  be  paved  or  lined  with  masonry.  The  safest  dis- 
position for  the  wasteway  is  at  some  favorable  point  in  the 
rim  of  the  reservoir  entirely  free  and  away  from  the  dam. 
This  may  be  through  some  low  saddle,  which  if  too  low  may 
be  filled  in  with  a  waste  weir  of  masonry,  or  if  too  high 
may  be  excavated  to  the  proper  elevation.  Such  an  isolated 
channel  is  frequently  found  beyond  some  spur  immediately 
adjacent  to  one  end  of  the  dam  and  discharging  back  through 
a  separate  channel.  This  is  the  case  in  the  Oak  Ridge  reser- 


EXAMPLES   OF    WASTEWAYS.  30$ 

voir  dam  in  New  Jersey,  the  Ashti  and  Periar  dams  in  India, 
and  the  Pecos  and  Idaho  dams  in  the  West. 

287.  Shapes  of  Waste  Weirs. — The  forms  of  waste  weirs 
for    dams    vary   considerably   with    the    circumstances    under 
which  they  are  constructed.     Their  general  design  is  very  sim- 
ilar to  that  of  weirs  used  for  purposes  of  diversion  and  thor- 
oughly discussed  in  Chapter  XII.     It  is  therefore  unnecessary 
here  to  enter  into  any  general  discussion  of  the  thickness  and 
dimensions  of  waste  weirs  or  their  shapes.     They  may  be  given 
the  ogee   shape  (Article   137)  in  order  that  the  water  falling 
over  them  shall  produce  the  least  vibration  in  the  structure  ; 
or  water-cushions  may  be  employed  to  deaden  the  effect  of 
the  falling  water  (Article  138). 

288.  Examples  of  Wasteways. — Brief  descriptions  and 
illustrations  of  wasteways  were  given  in  Articles  269  to  273. 
The  wasteway  of  the  Sweetwater  dam  is  peculiar.     It  is  built 
as  a  continuation  of  the  main  dam  and,  as  shown  in  Plates 
XXIV  and   XXV,  the  water  from  the  reservoir  enters  the 
several  separate    passageways   over   a  waste  weir   and    drops 
into  a  shallow  water-cushion.     Thence  it  flows  through  a  chan- 
nel partly  excavated  in  the  side  of  the  ravine  and  partly  con- 
structed by  means  of  an  artificial  wall  which  carries  the  water 
clear  of  the  toe  of  the   dam.     The  wasteways  to   the   Periar 
dam  are  two  in  number,  one  at  either  end  of  the  structure  ; 
both  are  separated  from  the  main  dam  by  means  of  low  sad- 
dles of  rock.     That  on  the  right  bank  is  cut  down  for  a  length 
of  420  feet  till  its  crest  is  11  feet  below  that  of  the  main  dam. 
On  the  left   bank  the  solid  rock  is  50  feet  below  the  crest  of 
the  dam,  and  the  saddle  is  closed  with  a  waste  weir  of  ma- 
sonry (Fig.  84)  built   up  to   the  same  level    as   that    of   the 
wasteway  on  the  other  bank.     At  a  distance  of  60  feet  from 
this  waste  weir  is  built  a  low  subsidiary  weir  10  feet  in  height 
with  its  crest  30  feet  below  the   upper  wall,  thus  forming  a 
water-cushion  on  which  the  floods  fall.     This  escape  weir  is  so 
designed  that  the  lines  of  pressure  fall  within  the  middle  third 
when  a  depth  of  12  feet  of  water  is  passing  over  the  crest,  and 


3O6  WAS TE  WA  YS  A ND   OUTLET  SL VICES. 

so  that  the  water  shall  fall  clear  of  the  weir  to  the  water-cushion 
below. 

A  similar  waste  weir  to  that  just  described  and  one  some- 
what similarly  situated  is  that  at  the  Idaho  Mining  and  Irriga- 
tion Company's  dam  described  in  Article  240.  The  wasteway 
of  the  Ashti  tank  in  India  consists  of  a  channel  having  a  clear 
width  of  800  feet  excavated  through  a  saddle  in  the  high  ridge 
bounding  the  reservoir  on  its  western  side.  The  bed  of  this 
channel  at  its  entrance  forms  the  weir  crest  and  is  level  for  a 
length  of  about  600  feet  and  then  falls  away  with  a  slope  of 
I  in  100  to  a  side  drainage  channel.  The  dam  is  12  feet  in 
height  above  the  crest  of  the  wasteway  and  the  greatest  flood 
anticipated  would  raise  the  water  in  this  wasteway  to  7  feet 
above  its  crest  or  to  within  5  feet  of  the  top  of  the  dam — just 
sufficient  to  prevent  waves  from  topping  it. 

289.  Automatic  Shutters  and  Gates. — The  use  of  flash- 
boards  or  any  similar  permanent  obstruction  in  a  wasteway  in 
order  to  increase  the  storage  capacity  of  the  reservoir  is  greatly 
to  be  condemned.  Such  obstructions  must  be  removed  at  the 
time  of  great  floods  or  else  these  will  top  the  dam.  The  result 
of  their  use  is  that  the  area  of  the  wasteway  is  diminished  below 
the  point  of  safety,  while  the  integrity  of  the  structure  depends 
upon  the  careful  attention  of  the  watchmen,  who  should  remove 
the  flashboards.  Automatic  shutters,  however,  have  been  used 
with  considerable  success  in  a  few  instances.  These,  however, 
should  only  be  employed  where  water  is  of  the  greatest  value 
and  the  saving  of  every  drop  is  essential. 

One  of  the  most  desirable  forms  of  these  is  that  shown  in 
Fig.  93.  It  consists  of  a  row  of  upright  iron  shutters,  each 
1 8  feet  long  and  22  inches  high.  These  are  supported  by 
struts  or  tension  rods  hinged  to  the  crest  of  the  weir  on  the 
up-stream  side  and  to  the  upper  side  of  the  shutter  at  about 
two  thirds  of  the  distance  from  its  crest,  or,  in  other  words, 
below  its  centre  of  gravity.  As  soon  as  the  water  level  ap- 
proaches the  top  of  the  shutter  it  causes  its  lower  end  to  slide 
inward  and  the  whole  falls  flat  against  the  top  of  the  weir, 
offering  no  obstruction  to  the  passage  of  the  water. 


AUTOMATIC   SHUTTERS  AND    GATES. 


307 


An  ingenious  form  of  automatic  weir  gate  (PL  XXIX)  was 
devised  and  patented  by  Mr.  E.  K.  Reinold  for  use  on  the 
Bhatgur  reservoir  in  India.  This  gate  is  of  value  where  water 
is  precious,  and  can  be  utilized  with  considerable  safety  to 
retain  water  to  the  full  storage  capacity  of  the  reservoir.  The 
gate  falls  automatically  as  soon  as  the  water  reaches  its  crest, 
and  continues  to  fall  as  the  flood  rises  until  the  full  discharge 
capacity  of  the  wasteway  is  brought  into  action.  The  gate 
then  closes  as  the  flood  subsides,  enabling  the  reservoir  to 
retain  the  maximum  amount  of  water. 

The  gate  slides  vertically  on  two  contact  surfaces  one  of 
which  is  the  face  of  the  wasteway  against  which  it  presses 
while  the  other  surface  is  attached  to  the  face  of  the  gate. 
These  surfaces  slide  parallel  to  each  other  and  are  the  sur- 
faces of  inclined  planes.  The  gate  rests  on  wheels  running  on 
rails,  and  the  axes  of  the  wheels  are  parallel  to  the  line  of  the 
rails  and  at  a  slight  angle  to  the  contact  planes  (PL  XXIX), 


Up  stream  slope 


FIG.  93. — CROSS-SECTION  OF  SHUTTER  ON  SOANE  WEIR,  INDIA. 

so  that  the  latter  do  not  touch  until  the  gate  is  fully  raised 
or  closed,  thus  permitting  by  leakage  a  large  amount  of  flood 
water  to  run  out  of  them  until  the  last  moment.  The  gates 
are  operated  by  means  of  counterpoises  balanced  in  water 
cisterns,  the  weight  of  these  counterpoises  exceeding  the  weight 
of  the  gate  by  a  little  more  than  the  amount  of  friction, 
and  they  act  by  displacing  their  volume  in  the  water  cisterns 
in  which  they  plunge,  thus  lessening  their  weight  by  that 
volume  of  water.  As  the  water  flows  over  the  top  of  the  gate 
it  simultaneously  enters  the  cast-iron  cisterns  in  which  the 
counterweights  hang.  When  the  water  ceases  to  enter  the 
cisterns  owing  to  its  level  having  fallen  below  that  of  the  inlets, 


3O8  WASTE  WAYS   AND     OUTLET  SLUICES. 

to/.*" 


' UNDERSLUICES.  309 

it  runs  out  from  holes  in  the  bottom  and  the  weights  then  be- 
come heavier  than  the  gate  and  raise  it. 

290.  Undersluices. — Undersluices  perform  the  same  func- 
tion for  storage  dams  as  do  scouring  sluices  in  diversion  weirs. 
Their  object  is  to  remove  or  to  prevent  the  deposition  of  sedi- 
ment in  the  reservoir.     Undersluices  have  little  effect  in  pre- 
venting the  deposition  of  silt  unless  the  area  of  their  opening 
is  great  compared  to  the  area  of  the  flood,  while  they  are  use- 
less for  the  removal  of  silt  already  deposited.     This  is  shown 
by  the  manner  in  which  such  reservoirs  as  Lake  Fife  and  the 
Vir  reservoir  in  Bombay,  India,  and  the  Folsom  reservoir  in 
California  have  silted  up  in  spite  of  them.     If  the  dam  is  high 
and    the   discharge    through   the    undersluices  will  keep  the 
flood  level  below  the  full  supply  level,  they  may  be  efficient  in 
preventing  the  deposit  of  silt  by  carrying  it  off  in  suspension. 
If  the  dam  is  low  and  the  area  of  the  undersluices  will  not  en- 
able them  to  keep  the  flood-level  below  full-supply  level,  they 
will  have  but  little  effect.     This  has  been  partly  proved  at 
the  Betwa  and  Bhatgur  reservoirs  in  India,  where  experience 
shows  that  their  scouring  or  preventive  effect  is  felt  but  a  few 
feet  to  either  side  of  the  sluice,  and  silt  will  deposit  close  to 
the   entrance.     In    other   words,  undersluices    do  little   more 
than  keep  an  open  channel  above  them. 

291.  Examples   of  Undersluices. — The  most  successful 
attempt  to  utilize  undersluices  for  the  clearance  of  silt  is  at  the 
Bhatgur  reservoir  in  India.     There  are  fifteen  undersluices  in 
the  centre  of  the  dam  near  its  bottom,  their  sills  being  60  feet 
below  high-water  mark  (PL  XXII).    Each  of  these  undersluices 
is  4  by  8  feet  in  interior  dimensions,  and  they  are  lined  through- 
out with  the  best  ashlar  masonry.     Under  a  full  head  they  will 
discharge  20,000  second-feet,  and  the  velocity  through  them  is 
36  feet  per  second.     Each  undersluice  is  closed  by  a  heavy 
iron  gate  which   slides  vertically  and   weighs   about    2   tons. 
They  are  operated  by  steel  screws  worked  from  above  by  a 
female  capstan  screw  turned  by  hand  levers.     Stout  wooden 
gratings    protect    the   gates    from   injury  by  floating   objects. 
The  undersluices   are    placed    about   30  feet   apart,  and  this 


310  WASTE  WAYS  AND   OUTLET  SLUICED. 

space  was  filled  with  sediment  shortly  after  the  completion  of 
the  dam. 

In  the  bottom  of  the  Folsom  dam  in  California  there  is  a  set 
of  three  undersluices,  the  object  of  which  is  to  remove  silt  depos- 
ited in  the  reservoir  (PL  XXVIII).  These  undersluices  are  built 
in  the  centre  of  the  weir  near  its  bottom  and  are  under  a  head 
of  60  feet,  the  area  of  each  one  being  4  by  4  feet.  While  these 
undersluices  have  not  impaired  the  integrity  of  the  structure, 
they  have  been  of  little  service  in  preventing  the  deposit  of 
silt,  as  their  area  compared  with  that  of  the  floods  is  compara- 
tively small.  Where  undersluices  have  been  employed  to  carry 
away  silt-laden  waters  from  in  front  of  a  canal  head  they  have 
proved  more  effective.  In  the  bottom  of  the  Idaho  Mining 
Company's  dam  an  undersluice  is  projected  the  sill  of  which  will 
be  13  feet  below  the  headgates  of  the  canal  and  24  below  the 
crest  of  the  dam.  It  will  be  4  feet  wide  by  8  feet  high  inside, 
closed  by  a  gate  operated  by  a  screw  from  the  top  of  the 
dam.  A  similar  under  or  scouring  sluice  is  built  in  the  bottom 
of  the  Pecos  dam  adjacent  to  the  entrance  to  the  canal  head. 

292.  Outlet  Sluices. — As  the  object  of  a  storage  dam 
is  to  impound  water  that  it  may  be  drawn  off  when  wanted, 
one  or  more  outlet  sluices  must  be  constructed  at  the  level 
at  which  water  can  be  drawn  off.  These  outlet  sluices 
either  terminate  in  pipe  lines  which  carry  the  water  to  the 
point  of  distribution  or  discharge  directly  into  the  canal 
head  or  back  into  the  stream  channel,  to  be  again  diverted 
lower  down.  The  greater  the  depth  at  which  these  sluices  are 
placed,  the  greater  the  available  capacity  of  the  reservoir. 
They  may  either  be  built  in  the  body  of  the  dam  or  through 
the  confining  hillsides  independently  of  the  dam.  The  latter 
is  by  far  the  better  and  safer  method,  and  wherever  practicable 
should  be  employed,  as  anything  which  breaks  the  homo- 
geneity of  the  dam  is  a  menace  to  its  integrity.  With  an 
earth  dam  this  is  especially  true,  and  its  greatest  source  of 
weakness  is  the  masonry  discharge  conduit  passing  through  it. 
Simple  pipes  should  never  be  laid  through  an  earth  embank- 
ment, as  under  the  pressure  of  the  water  in  the  reservoir  this 


OUTLET  SLUICES.  311 

is  certain  ultimately  to  find  its  way  along  the  line  between  the 
pipe  and  the  earth  embankment  or  through  a  loose  joint  in 
the  pipe,  and  the  water  which  enters  the  embankment  in  this 
manner  will  rapidly  increase  in  quantity  until  the  structure  is 
destroyed. 

It  is  essential  that  the  outlet  sluices,  valves,  pipes,  etc.r 
should  always  be  accessible  for  inspection  and  repair  in  order 
that  the  constant  use  of  the  reservoir  may  not  be  interrupted. 
When  they  must  be  placed  in  the  embankment  a  masonry  con- 
duit should  be  built  through  it,  and  for  convenience  of  inspec- 
tion an  iron  pipe  should  be  placed  in  this.  The  conduit  should 
be  of  such  dimensions  that  a  man  can  pass  through  it,  and  the 
pipe  should  be  so  placed  within  it  as  to  be  easily  seen  and  re- 
paired. In  order  to  prevent  the  travel  of  seepage  water  along 
the  outside  of  the  conduit,  rings  of  masonry  should  be  placed 
at  short  intervals  along  its  length,  and  these  should  project 
not  less  than  from  I  to  2  feet  from  its  surface.  The  chief 
objection  to  laying  a  conduit  through  a  dam  is  its  liability  to 
fracture  through  settlement. 

Better  and  safer  than  this  is  to  lay  the  discharge  pipes  in  a 
trench  dug  under  the  foundation  of  the  dam  in  the  surface 
rock  or  soil.  Such  a  trench  should  be  substantially  lined  and 
roofed  with  concrete,  and  will  offer  little  inducement  for  travel 
of  seepage  water.  The  best  method  of  all,  however,  for  the 
placing  of  outlet  pipes  is  to  build  them  through  the  surface 
rock  or  soil  of  the  country,  excavating  a  tunnel  for  this  pur- 
pose and  laying  the  pipes  in  it,  the  whole  being  away  from 
and  independent  of  the  dam.  This  insures  them  against  any 
damage  from  settlement  in  the  structure. 

Sometimes  the  entrance  to  the  outlet  culvert  is  not  placed 
at  the  lowest  level  of  the  reservoir,  but  at  about  two  thirds 
the  way  up  the  embankment  from  the  bottom,  or  at  such 
height  that  the  pressure  will  enable  a  siphon  to  draw  water 
off  from  the  lowest  depths  of  the  reservoir.  This  siphon  pipe 
is  carried  down  to  the  bottom  of  the  reservoir  and  passes 
up  through  the  culvert  in  which  is  placed  the  main  pipe  con- 
nected with  the  valve  chamber  and  supplied  directly  from 


312  WASTEWAYS  AND   OUTLET  SLUICES. 

orifices  above  the  level  of  the  conduit  (Fig.  94).  Where  a 
reservoir  embankment  is  very  low — say  25  feet  or  under — it  may 
be  discharged  by  simply  carrying  a  siphon  pipe  over  the  top  of 
the  embankment  with  no  outlet  pipe  or  conduit  through  the 
embankment. 


FIG.  94. — CROSS-SECTION  OF  EARTH  DAM 

293.  Gate  Towers  and  Valve  Chambers.— The  valves 
.or  controlling  the  admission  of  water  to  the  outlet  sluice  are 
either  operated  from  a  valve  chamber  let  into  the  body  of  the 
dam  or  from  a  gate  tower  situated  in  the  reservoir  at  a  point 
vertically  over  the  inlet  to  the  discharge  conduit.  In  order 
that  these  valves  shall  not  be  worked  under  too  great  pressure, 
water  is  usually  admitted  to  the  tower  or  well  from  orifices 
placed  at  several  depths,  and  in  this  well  the  conduit  heads.  At 
its  exit  at  the  lower  side  of  the  dam  is  generally  placed  a  second 
valve  chamber  or  gatehouse  for  the  control  of  water  which  is 
admitted  to  the  distributing  pipes  or  canal.  The  orifices  ad- 
mitting water  to  the  well  tower  are  closed  on  the  outside  by 
plugs  or  close-fitting  valves  which  can  be  operated  from  the  top 
of  the  tower  or  valve  chamber ;  while  the  valve  admitting  the 
water  from  the  bottom  of  the  well  to  the  outlet  sluices  is 
operated  either  from  the  tower  or  from  the  bottom  of  the  well 
pit  by  screws  and  hand  gearing.  In  this  manner  the  attendant 
in  charge  has  full  control  of  the  whole  outlet  works,  and  all 
pipes  and  valves  are  under  perfect  control  so  that  the  supply 
can  at  any  time  be  arrested  for  the  repair  of  pipes.  In  case  a 
gate  tower  is  constructed  independently  of  and  away  from  the 
body  of  the  dam,  great  care  must  be  taken  to  make  it  suffi- 
ciently substantial  to  withstand  the  thrust  of  ice,  or  it  should 
be  buttressed  against  the  side  of  the  dam. 


GATE    TOWERS  AND    VALVE   CHAMBERS.  313 

The  outlet  sluicepipe  which  passes  through  the  embank- 
ment may  be  connected  on  the  inside  of  the  reservoir  by  a 
flexible  joint  with  another  pipe  of  the  same  diameter,  to  the 
end  of  which  is  attached  a  float.  This  pipe  can  thus  be  moved 
vertically,  and  admits  of  the  water  being  drawn  off  from  the 
surface  where  the  pressure  on  the  valve  is  the  least.  Where 
the  expense  will  permit,  the  better  method  is  that  of  admitting 
the  water  to  a  valve  well  through  orifices  situated  at  varying 
heights.  One  of  the  great  difficulties  encountered  is  to  insure  a 
constant  discharge  from  the  reservoir  with  a  constantly  vary- 
ing head  in  it  or  in  the  gate  well.  The  usual  method  of  insur- 
ing a  constant  discharge  is  by  opening  the  valve  gates  control- 
ling the  admission  of  water  to  the  outlet  sluice  to  a  greater  or 
less  extent  according  to  the  amount  of  water  required,  though 
automatic  systems  of  maintaining  a  constant  discharge  irre- 
spective of  the  head  have  been  used  with  more  or  less  success 
in  a  few  cases.  The  inlets  to  the  valve  chamber  are  of  two 
general  classes.  That  illustrated  in  Fig.  95  is  of  the  kind  em- 


FIG.  95.— VALVE-PLUG,  SWEETWATER  DAM. 

ployed  on  the  Sweetwater  dam  in  California,  and  consists  of  a 
simple  cast-iron  plug  let  into  the  top  of  the  pipe,  the  end  of 
which  is  bent  upward.  This  plug  is  held  in  position  by  the 
pressure  of  the  water  and  is  removed  by  a  chain  operated  from 
above  by  a  windlass.  In  Plate  XXV  is  shown  the  method  of 
placing  the  valves  at  varying  heights  and  the  arrangement  of 
air  valve  and  gatehouse  at  the  lower  end  of  the  dam. 

Another  method  of  admitting  water  to  the  valve  chamber 
is  by  means  of  rectangular  openings  in  the  side  of  the  chamber 
on  the  inner  surface  of  which  stop  valves  are  bolted.  These 
are  usually  of  cast-iron,  the  seat  and  bearing  of  the  valve  being 
faced  with  bronze  composition.  Above  this  projects  a  screw 


WASTEWAYS  AND    OUTLET  SLUICES. 

stem  which  is  operated  from  above  by  means  of  a  female  cap- 
stan screw.  Where  the  area  of  such  valves  exceeds  4  or  5 
square  feet  or  the  pressure  is  more  than  20  to  25  pounds,  some 
geared  motion  is  usually  necessary  to  enable  a  single  man  to 
operate  it.  The  intake  valve  permitting  the  water  to  pass  from 
the  valve  chamber  to  the  outlet  sluice  is  usually  a  sliding  valve, 
working  on  bronze  bearings  and  operated  from  above  by  a 
screw  and  hand  gearing.  It  is  not  unusual  to  employ  more 
than  one  such  valve,  according  to  the  amount  of  water  to  be 
admitted  and  the  consequent  number  of  outlet  pipes  required. 
The  foundations  for  gate  towers  must  be  of  the  most  substan- 
tial character,  especially  where  they  are  attached  to  loose  rock 
or  earth  dams, — in  which  case  the  foundation  must  be  carried 
down  to  a  sufficient  depth  to  insure  stability. 

294.  Examples  of  Gate  Towers  and  Outlet  Sluices.— 
Owing  to  the  low  inclination  of  the  inner  surface  of  earth  em- 
bankments or  loose-rock  dams,  it  is  necessary  to  construct  the 
gate  tower  controlling  the  outlet  sluice  at  some  little  distance 
in  the  reservoir  so  that  it  shall  come  above  the  entrance  to  the 
sluice.  This  method  of  construction  is  occasionally  employed 
on  masonry  dams,  and  an  excellent  example  of  such  a  work  is 
that  illustrated  in  Plates  XXIV  and  XXV,  showing  the  gate 
tower  to  the  Sweetwater  reservoir.  In  Fig.  96  are  shown  in 
plan  and  cross-section  the  arrangement  of  the  valve  chamber 
and  intakes  of  the  proposed  Bear  Valley  dam  in  California. 
As  will  be  noticed,  the  valve  chamber  or  tower  is  built  of 
masonry  as  a  projection  on  the  inner  surface  of  the  dam,  thus 
becoming  practically  agate  tower  attached  to  the  centre  of  the 
dam.  The  intake  valves  in  this  case  are  similar  to  those  em- 
ployed in  the  Sweetwater  dam,  and  discharge  directly  into  a 
valve  well. 

A  much  better  practice,  however,  is  that  followed  on  the 
Vyrnwy  dam  in  Wales  and  the  San  Mateo  dam  in  California. 
In  the  case  of  the  former  there  are  two  discharge  sluices 
operated  from  valve-houses  built  in  the  body  of  the  dam  for 
discharging  compensation  water  back  into  the  stream.  The 
main  valve  chamber,  however,  for  the  supply  of  water  to  the 
aqueduct  is  situated  at  a  point  on  the  shore  of  the  reservoir 


GATE    TOWERS  AND   OUTLET  SLUICES. 


315 


about  three  fourths  of  a  mile  distant  from  the  dam ;  entirely 
independent  of  it,  and  out  in  the  lake  at  such  a  distance  as  to 
control  water  at  nearly  the  maximum  depth.  The  valves  and 
other  mechanisms  employed  in  this  tower  are  all  operated  by 
hydraulic  power  furnished  from  a  water-wheel  supplied  by  a 
small  mountain  reservoir.  In  the  case  of  the  San  Mateo  dam 
(PL  XXIII),  and  the  proposed  Citizens*  Water  Company  dam  in 
Colorado,  the  valve  tower  is  situated  at  a  point  quite  independ- 


FIG.  96. — VALVE  CHAMBER  AND  VALVES. 

ent  of  the  dam,  and  the  outlet  conduit  passes  through  the 
country  rock  at  a  sufficient  distance  from  the  abutments  of  the 
structure  to  be  entirely  free  from  the  pressure  of  its  possible 
subsidence.  As  shown  in  the  illustration,  water  is  admitted  at 
three  different  elevations  through  inle^  pipes  which  discharge 
directly  into  a  main  iron  standpipe  passing  vertically  through 
a  shaft  which  is  the  entire  height  of  the  dam.  The  entrance 
of  this  water  to  the  standpipe  is  controlled  by  plunger  valves 
operated  by  hand  wheels  and  approached  by  a  stairway  passing 
through  the  tower.  At  the  outer  end  of  the  discharge  pipe  is 
another  gate-well  where  the  main  supply  is  regulated. 


CHAPTER   XXI. 
PUMPING,  TOOLS,  AND   MAINTENANCE. 

295.  Underground  Cribwork  or  Tunnels. — Submerged 
cribs  have  been  satisfactorily  employed  by  the  American 
Water  Company  on  Cherry  creek  in  Colorado,  and  by  the 
Citizens'  Water  Company  on  the  South  Fork  of  the  Platte 
river  in  Colorado.  The  former  enterprise  consists  of  a  sub- 
merged open  crib  dam  sunk  in  the  gravel  bed  of  Cherry  creek, 


FIG.  97.— GATHERING-CRIBS,  CITIZENS'  WATER  Co.,  DENVER. 

and  resting  on  solid  rock  which  is  73  feet  below  the  surface  of 
the  stream.  This  cribwork  is  70  feet  in  height,  and  its  crest 
is  3  feet  below  the  bed  of  the  stream.  This  is  not  a  dam,  as  it. 

316 


T  UNNELLING—P  UMPING.  3 1  / 

does  not  extend  across  the  entire  channel  of  the  stream,  but  it 
stops  the  movement  of  that  portion  of  the  subsurface  water 
which  enters  the  cribwork.  This  is  open  on  the  upper  side 
but  closed  on  the  down-stream  side,  and  consists  of  timbers  14 
inches  in  dimension  at  the  bottom  of  the  dam,  which  is  de- 
creased to  8  inches  at  the  top.  These  timbers  are  placed  4 
feet  apart  across  stream,  and  are  planked  on  both  faces  with 
interstices  of  3  inches  on  the  upper  face.  The  water  caught  in 
this  cribwork  is  pumped  to  the  surface. 

The  Citizens'  Water  Company  develope  the  underground 
waters  of  the  Platte  river  by  means  of  a  series  of  gathering 
galleries,  consisting  of  perforated  pipe  and  open  cribwork  laid 
at  a  depth  of  from  14  to  22  feet  below  the  surface  of  the  gravel 
bed  of  the  stream.  The  cribs  (Fig.  97)  are  30  inches  square, 
and  about  a  mile  of  these  have  been  built  running  up  the  bed 
of  the  stream,  besides  about  a  mile  of  perforated  pipe  30  inches 
in  diameter.  The  average  daily  yield  obtained  by  these  gal- 
leries is  nearly  10  acre-feet  of  water,  which  is  led  off  through 
the  pipes  by  natural  flow. 

296.  Tunnelling  Underground. — For  the  development  of 
underground  waters,  tunnelling,  which  is  a  little  different  from 
the  cribwork  just  described,  has  been  resorted  to  in  a  few  in- 
stances.    For  the  development  of  the  water  supply  of  Ontario 
Colony  (Art.  42),  and  at  the  mouth  of  the  Santa  Anna  river  in 
California,  tunnels  have  been  built  under  the  stream  bed,  the 
cross-section  of  these  being  trifling,  and  the  tops  roofed  by  open 
lagging,  while  the  sides  and  bottom  are  formed  into  an  imper- 
vious channel  by  a  framing  of  woodwork  or  a  cement  lining. 
The  seepage  water  which  enters  these  tunnels  is  led  off  through 
open  cuts,  and  is  let  into  the  irrigating  ditches. 

297.  Pumping  or  Lift  Irrigation. — The  methods  of  irri- 
gation  heretofore  considered    are  those    in  which  the  water 
reaches  the  irrigable  land  by  means  of  gravity  or  natural  flow. 
Frequently,  however,  there  are  large  volumes  of  water  which 
are  situated  at  such  low  levels  that  gravity  will  not  carry  them 
to   the  field  to  be  irrigated,    and   this  water  must  be  raised 
or  lifted  by  means  of  pumps  or  other  lifting  devices.     Lift 


3l8  PUMPING,    TOOLS,    AND   MAINTENANCE. 

irrigation  may  be  employed  to  utilize  the  water  from  wells  or 
from  natural  streams  flowing  at  a  lower  level  than  the  field 
worked,  or  it  may  be  employed  to  raise  water  from  the  canals 
to  higher  levels  than  those  reached  by  them. 

When  the  gravity  sources  of  supply  have  been  entirely 
utilized,  large  areas  of  land  may  still  be  brought  under  cultiva- 
tion by  the  employment  of  pumps.  As  irrigation  is  practised 
the  subsurface  soil  becomes  saturated,  the  ground-water  level 
is  raised,  and  much  of  the  water  which  is  delivered  by  gravity 
systems  may  by  pumped  up  and  re-employed  for  irrigation, 
thus  greatly  adding  to  the  duty  of  the  ultimate  sources  of 
water  supply.  The  value  of  pumping  for  this  purpose  has 
been  recognized  in  the  older  European  and  Asiatic  countries 
for  ages.  A  very  large  proportion  of  the  irrigation  in  Europe, 
China,  Japan,  India,  and  Egypt  is  by  means  of  lifting.  Among 
the  various  methods  more  commonly  practised  in  Asia  for 
lifting  water  from  wells  are  the  Mot  of  India,  which  consists  of 
a  rope  passing  over  a  pulley  down  into  the  well  and  to  the 
bottom  of  which  a  bucket  or  other  receptacle  is  attached. 
This  is  raised  by  two  bullocks  walking  away  with  the  rope  and 
raising  the  bucket  to  the  top  of  the  well,  where  it  is  emptied 
into  the  distributing  ditches.  One  of  the  more  common 
methods  of  pumping  is  by  means  of  the  Persian  Wheel,  which 
consists  of  a  vertical  wheel  on  the  outer  rim  of  which  are  at- 
tached buckets  which  dip  into  a  well,  and  as  they  reach  the 
upper  circumference  of  the  wheel  spill  their  water  into  a  trough 
which  leads  it  to  the  fields.  This  wheel  is  made  to  revolve  by 
means  of  bullock  walking  in  a  circle  and  drawing  a  sweep 
attached  to  rough,  cogged  gearing.  By  this  means  two  bullocks 
are  estimated  as  capable  of  lifting  2000  cubic  feet  of  water  per 
day.  Still  another  method  of  lifting  water  is  by  means  of 
the  Paecottah,  which  is  simply  the  old-fashioned  well-sweep 
of  this  country.  By  its  use  from  400  to  2000  cubic  feet  of 
water  can  be  raised  a  day,  while  with  the  Mot,  two  bullocks 
working  10  hours  a  day  will  raise  about  3f  acre-feet  of  water 
in  a  season  of  90  days. 

In  this  country  the  value  of  pumping  as  a  means  of  irri- 


WINDMILLS  AND    WATER-WHEELS.  319 

gation  is  not  yet  fully  appreciated  :  a  few  windmills  and  water 
wheels  are  utilized  for  this  purpose,  and  some  small  amount 
of  pumping  is  done  by  steam-power,  though  the  value  of  the 
water  supply  to  be  derived  from  the  latter  mode  of  lifting 
is  destined  to  increase  greatly  in  the  near  future. 

298.  Windmills  and  Elevators. — Windmills  have  been 
extensively  used  in  the  San  Joaquin  valley  in  California  and 
in  a  few  places  in  the  Colorado  plains  and  elsewhere  in  the 
West  for  raising  water  for  purposes  of  irrigation.  As  yet  they 
have  been  employed  chiefly  for  pumping  for  domestic  uses, 
but  as  water  becomes  more  valuable  windmills  are  rinding 
greater  favor.  Most  of  these  machines  are  patented,  and  the 
makers  furnish  all  the  information  desired  relative  to  their 
cost,  capacity,  and  duty.  A  modern  ten-foot  wheel  will  average 
about  one  eighth  horse-power  developed  for  a  stiff  breeze  and 
will  cost  about  six  cents  per  horse-power  per  hour.  Larger 
wheels  are  much  cheaper.  A  fifteen-foot  wheel  will  irrigate 
about  seven  acres  at  a  cost  of  $8  per  acre  per  annum. 

A  link-belt  water  elevator  manufactured  in  Chicago  has 
been  successfully  employed  in  the  West  for  raising  water  for 
irrigation.  It  is  operated  by  horse-power,  and  consists  of  a 
link  belt  erected  at  a  slight  inclination  from  the  vertical  and 
revolving  over  two  wheels,  one  pivoted  a  little  below  the  level 
of  the  water  surface  and  the  other  at  the  summit  of  the  height 
to  which  the  water  is  to  be  lifted.  On  this  belt  are  a  number 
of  iron  vanes  attached  at  intervals  of  about  8  inches  apart,  and 
these  pass  up  through  a  closed  wooden  boxing,  so  that  each 
vane  acts  as  a  lift  and  raises  the  water  above  it,  as  does  the  old 
chain  pump  used  in  shallow  wells.  This  water  is  emptied  out 
through  a  lip  to  a  flume,  from  which  it  runs  to  the  irrigated 
lands.  With  a  belt  speed  of  300  feet  the  smallest  of  these 
elevators  will  raise  about  20  cubic  feet  per  minute  to  a  height 
of  10  feet ;  the  largest  will  elevate  nearly  5  second-feet  of 
water  to  the  same  height. 

209.  Water-wheels. — Lifting  water  by  means  of  under- 
shot water-wheels  has  been  practised  ever  since  the  early 
placer  operations  in  California,  while  in  the  older  countries 


320 


PUMPING,    TOOLS,    AND   MAINTENANCE. 


this  method  of  lifting  water  is  extremely  ancient.  The  Noria 
of  Italy  is  simply  an  undershot  water-wheel  of  this  description. 
As  used  in  a  few  occasional  instances  in  the  West,  these  wheels 
are  very  similar  in  appearance  to  an  old  steamboat  paddle- 
wheel,  varying  from  15  to  20  feet  in  diameter,  the  width  of  the 
wheel  or  the  length  of  the  paddles  being  from  6  to  10  feet. 
Such  a  wheel  (Fig.  98)  will  rest  either  on  cribwork  abutting  on 
the  shores  and  in  the  river,  or  if  the  change  in  the  flood  height 
of  the  river  is  considerable  it  may  rest  on  some  variety  of 


FIG.  98.— VIEW  OF  WATER-WHEEL. 

anchored  float  which  will  permit  it  to  rise  and  fall  with  the 
stream.  On  the  outer  circumference  of  these  wheels  are 
placed  a  series  of  buckets,  one  attached  to  each  blade  or 
paddle.  These  buckets  may  be  constructed  of  tin,  as  old  tin 
cans,  or  sometimes  are  constructed  of  wood,  and  as  the  wheel 
revolves  they  are  filled  as  they  are  successively  immersed* 


STEAM  PUMPS.  32T 

When  they  reach  such  a  point  in  their  revolution  that  the 
water  begins  to  spill  out  of  them,  it  is  caught  in  a  trough 
suitably  placed,  and  from  this  runs  into  a  flume  which  leads  it 
to  the  fields. 

Some  of  the  water-wheels  of  this  variety  which  have  proved 
most  successful  on  the  Green  river  in  Colorado  are  from  20  to 
30  feet  in  diameter,  the  wooden  axle  being  5  inches  in  diame- 
ter, while  the  paddles  dip  about  2  feet  into  the  water  of  the 
stream.  The  buckets,  which  are  of  wood,  have  an  air-hole  in 
the  bottom  closed  by  a  suitable  leather  valve  which  permits  of 
the  bucket  being  rapidly  filled  by  forcing  out  the  air.  These 
buckets  are  of  wood,  about  6  feet  in  length  and  4  inches  square, 
the  capacity  of  each  being  about  5  gallons.  There  are  sixteen 
paddles,  to  each  of  which  is  attached  a  bucket,  thus  enabling 
one  revolution  of  the  wheel  to  lift  So  gallons.  The  wheels 
make  about  two  revolutions  a  minute,  but  as  a  large  percentage 
of  the  water  raised  is  spilled  in  emptying  into  the  flume,  each 
wheel  has  been  found  to  handle  about  4000  cubic  feet  a  day. 

300.  Steam  Pumps. — The  value  of  steam  pumps  for  pur- 
poses of  irrigation  is  not  fully  appreciated.  There  are  many 
places  where  water  can  be  pumped  at  comparatively  small  cost, 
and  yet  where  the  land  it  will  serve  must  otherwise  remain 
uncultivated  but  for  water  obtained  by  this  means.  Steam 
pumping  for  irrigation  has  been  practised  to  a  limited  extent 
in  Colorado,  in  Arizona,  and  in  California,  and  many  varieties 
of  pumps  have  been  employed  for  this  purpose.  It  is  not  the 
intention  in  a  work  of  this  sort  to  describe  the  mechanical 
details  of  pumps,  the  value  of  each  type,  or  the  theories  and 
formulas  on  which  its  operation  and  coal  consumption  depend. 
These  can  all  be  found  fully  discussed  in  the  many  books  and 
pamphlets  which  have  been  written,  more  particularly  on  the 
subjects  of  "  Mine  Pumping"  and  "  Pumping  for  Waterworks," 
or  they  can  be  obtained  from  the  trade  catalogues  of  pump 
makers.  The  chief  point  of  difference  between  pumping  for 
irrigation  and  pumping  for  mines  and  waterworks  is  in  the 
height  to  which  the  water  has  to  be  forced.  For  purposes  of 
irrigation  it  has  rarely  to  be  lifted  to  heights  exceeding  25  or 


322  PUMPING,    TOOLS,    AND   MAINTENANCE. 

30  feet,  the  water  having  to  be  raised  generally  from  a  well  or 
river  merely  to  a  sufficient  height  to  enable  it  to  flow  to  the 
fields  by  the  action  of  gravity. 

In  a  few  notable  instances  it  has  been  necessary  to  force 
the  water  to  greater  heights.  In  one  case  near  Tucson,  Ari- 
zona, the  depth  of  the  well  is  about  70  feet,  and  the  water  has 
to  be  raised  this  height  to  bring  it  to  the  surface  of  the  ground. 
Perhaps  the  most  remarkable  instance  of  pumping  for  irriga- 
tion is  in  Italy,  above  Saluggia,  on  the  Cavour  canal.  In  this 
case  the  river  Dora  Baltea  runs  between  rather  high  banks,  and 
it  was  found  impossible  to  bring  water  to  the  highest  levels  by 
means  of  natural  flow.  Accordingly  the  water  that  is  taken 
from  the  river  by  one  of  the  canals  is  pumped  to  the  high  level, 
whence  it  flows  through  a  gravity  system  to  the  fields.  There 
.are  in  all  four  canal  levels  along  the  hillside.  Between  the 
two  lower  is  placed  an  extensive  pumping  plant  operated  by 
turbines,  which  receive  their  water  from  the  upper  of  these  two 
and  tail  into  the  lower  canal,  whence  the  water  is  distributed  to 
low-lying  fields.  The  lower  of  the  two  upper  canals  supplies 
water  by  means  of  an  immense  wrought-iron  pipe  3  feet  in 
diameter,  with  a  head  of  66  feet,  to  the  pumps  below,  and  these 
force  it  through  another  pipe  of  the  same  dimensions  a  total 
height  of  140  feet  to  the  high-level  or  distributive  canal.  The 
head  of  66  feet  on  the  pumps  practically  counterbalances  that 
height  in  the  140-foot  force-pipe. 

The  varieties  of  pumps  more  commonly  employed  in  the 
West  are  :  I.  Centrifugal  pumps,  which  for  their  operation  re- 
quire small  steam-engines  ;  2.  Vacuum  pumps,  pulsometers,  and 
a  variety  of  patented  pump  made  in  Greeley,  Colorado,  known 
as  the  Huffer  and  Nye  pumps ;  and,  3.  Pumping  engines. 

301.  Centrifugal  Pumps. — The  ordinary  centrifugal  pumps 
employed  for  irrigation  have  capacities  varying  between  500 
and  1 500  gallons  per  minute,  the  height  raised  ranging  from 
20  to  80  feet.  The  average  pump  handles  about  a  thousand 
gallons  a  minute  or  2  second-feet,  with  heights  of  from  25  to 
40  feet.  Such  a  pump  will  irrigate  from  5  to  10  acres  per  day, 
.and  in  the  course  of  an  irrigation  season  will  handle  about  too 


PUMPING  ENGINES.  323 

acres.  It  is  easily  operated  by  one  man,  and  the  cost  of 
maintenance  for  a  season  of  three  months  amounts  to  $2.50 
per  acre, — a  relatively  low  water  rate.  A  plant  of  this  kind 
erected,  including  engine,  boiler,  and  pumps,  costs  about  $1500 
—equivalent  to  a  first  cost  of  about  $15  per  acre. 

302.  Huffer  and   Nye  Pumps. — These  pumps  have  been 
used  in  large  numbers   in  Colorado,  Wyoming,  and  other  por- 
tions of  the  West.     Their  capacity  is  small,  averaging  about  400 
gallons  a  minute,  or  about  one  second-foot  of  water.    They  are 
capable   of  lifting   water   to  heights  of    15  to   20  feet,  and  of 
forcing  it  to  low  heights  not  exceeding  40  feet.     They  will 
irrigate   from   3  to  5   acres  per  day,  and   if  carefully  handled 
from  50  to  100  acres  in  a  season.     The  cost  of  operating  these 
pumps,  or  the  water  rate,  ranges  between  $3  and  $5  per  acre, 
while  the  first  cost  of  the  plant  erected  is  about  $1500,  or  from 
$15  to  $30  per  acre. 

303.  Pumping  Engines. — The  writer  is  strongly  in  favor 
of  the  use  of  steam  pumping  engines  in  preference  to  centrifu- 
gal pumps   or  any  of  the  peculiar    patented   varieties.     The 
regular  steam  pumping  engines,  such  as  those  made  by  Worth- 
ington;  Knowes;  Smith,  Vaile  &  Co.,  and  numerous  others, 
cost  little  or  no   more  than  the  varieties  of  pumps  just  men- 
tioned.    Their   maintenance    cost    is  no  higher,   especially  if 
compound  or  condensing  engines  are  employed,  while  for  large 
pumping  plants  they  are  much   cheaper.     Their  operation  re- 
quires more  skilled  labor  than  do   the  other  pumps  just  men- 
tioned, but  they  are  far  less  liable  to  get  out  of  order,  and  the 
injuries  can  be  more  readily  repaired.     A  high-pressure  pump- 
ing engine  which  the  writer  saw  in  operation   in  Arizona  was 
capable  of  irrigating  100  acres.     This  pump  cost  $1000  erected, 
and  its  running  expense  was  about  $5  per  half  second-foot  of 
water  raised.     Its  original  cost  was  about  $10  per  acre  irrigated, 
while  the    annual   charge  for  running  expenses  amounted  to 
about  $5  per  acre.     A  much  better  and  more  modern  plant, 
operated   near  Tucson,  Arizona,  by  Mr.  A.  Hartt,  consists  of 
two  compound  pumping  engines,  capable  of  irrigating  600  acres 
per  day  of  12  hours  at  a  cost  of  $3  per  day.     The  first  cost  of 


324  PUMPING,    TOOLS,    AND   MAINTENANCE. 

this  plant  laid  down  was  $4200,  while  the  well,  which  is  70  feet 
in  depth  through  quicksand,  cost  $5000.  Allowing  the  well  to 
have  been  of  average  cost,  the  whole  plant  would  have  cost  a 
little  over  $5000 — equivalent  to  a  charge  of  $8.50  per  acre. 
The  daily  working  expenses  are  about  $3  for  raising  5^- 
second-feet  a  height  of  70  feet — equivalent  to  an  annual  charge 
of  about  70  cents  per  acre. 

The  following  is  considered  by  the  writer  as  a  first-class 
pumping  plant  for  the  irrigation  of  about  1000  acres,  where 
the  water  is  to  be  pumped  directly  from  a  river  or  from  an  in- 
expensive well.  This  plant  should  consist  of  a  duplicate  set  of 
the  best  of  duplex  compound  pumping  engines  capable  of  rais- 
ing each  about  1200  gallons  per  minute,  with  a  suction  height 
not  greater  than  15  feet,  and  a  force  height  of  20  to  40  feet 
additional.  In  developing  the  irrigable  lands  from  such  a 
plant  as  this  a  boiler  capable  of  serving  both  pumps  should  be 
purchased  at  first,  but  only  one  pump  need  be  purchased  until 
sufficient  of  the  land  is  developed  to  necessitate  the  purchase 
of  the  other  pump.  Then  only  one  pump  will  be  required  for 
the  performance  of  the  requisite  service  during  much  of  the 
time,  the  other  being  a  duplicate  or  relay  pump  in  case  of  ac- 
cident. When,  however,  the  entire  property  is  to  be  irrigated,, 
both  pumps  will  be  called  upon  to  do  their  highest  duty. 
Such  a  pumping  plant  can  be  erected  in  nearly  any  portion  of 
the  West  for  about  $5000,  or  at  a  charge  of  $10  per  acre.  The 
cost  of  maintenance  and  operation  for  this  plant  should  not 
exceed  75  cents  an  acre,  which  is  much  lower  than  the  ordi- 
nary water  rates  for  gravity  systems. 

304.  Irrigation  Tools. — There  is  little  to  say  of  the  tools- 
required  in  the  construction  and  management  of  irrigation 
works.  The  only  tools  here  discussed  will  be  such  unusual 
mechanisms  as  special-shaped  ploughs  and  scrapers.  The  tool- 
makers  now  manufacture  hoes,  spades  and  shovels,  ploughs, 
and  scrapers,  of  special  designs  for  the  making  and  control  of 
ditches  and  furrows.  Special  ditching  ploughs  of  unusual 
depth  and  reach  are  made  as  right  and  left  ploughs,  or  some- 
times to  throw  dirt  in  both  directions,  having  a  V-shaped 


SCRAPERS. 


325 


shear,  thus  making  a  V-ditch  at  one  operation.     Ploughs  of 
this  kind  are  also  arranged  in  gangs  on  sulkies. 

Corrugated  ribbed  rollers  are  employed  where  the  surface  of 
the  country  is  even  and  level,  and  for  such  crops  as  grain  and 
alfalfa.  These  consist  essentially  of  a  roller  of  the  ordinary 
form,  on  the  outer  surface  of  which  are  iron  rings  or  projec- 
tions of  from  2  to  3  inches  in  height  and  of  about  the  same 
width,  placed  from  4  to  8  inches  apart.  These  projections  are 
sometimes  V-shaped.  In  running  this  roller  over  the  surface  of 
a  well-harrowed  field  it  leaves  small  furrows,  down  which  the 


FIG.  99.— BUCK  SCRAPER. 


water  runs,  thus  irrigating  the  crop  much  as  if  it  were  flooded. 
305.  Scrapers. — The  most  useful  implement  for  the  ditch 
and  canal  maker  is  the  scraper,  of  which  there  are  many  forms 
and  with  most  of  which  engineers  are  familiar.  Two  forms 
of  scrapers  which  have  peculiar  advantages  in  ditch-making 
over  the  ordinary  road  scraper  are  the  Fresno  and  Buck  scrap- 
ers. The  latter  is  especially  useful  in  sandy  soil  with  a  low  lift 
and  short  haul,  and  cheaper  work  has  been  done  with  it  than 
with  any  other  implement.  A  common  form  of  Buck  scraper 
consists  of  a  working  or  frond  board  with  an  effective  length  of 
about  9  feet  and  a  height  of  22  inches.  This  board  rests  hori- 
.zontally  on  edge  on  the  ground,  and  consists  of  two  planks  each 


326  PUMPING,    TOOLS,  AND  MAINTENANQE. 

2  inches  in  thickness,  below  which  is  fastened  an  iron  cutting 
edge  which  reaches  7  inches  lower  (Fig.  99).  At  either  end  of 
the  scraper  is  a  cam-shaped  roller  4  inches  in  height,  on  which 
the  scraper  is  turned  over.  This  board  is  fastened  at  the  back 
to  a  tailboard  3  feet  9  inches  in  length,  on  which  the  driver 
stands,  and  is  drawn  forward  by  from  two  to  four  horses,  the 
scraper  being  dumped  by  the  driver  merely  stepping  off  the 
tailboard,  the  forward  pull  upsetting  it.  This  implement  han- 
dles a  load  of  from  I  to  i£  cubic  yards,  while  its  average  daily 
capacity  is  about  130  cubic  yards.  For  two  horses  a  scraper  of 
this  form  is  rarely  made  over  6  feet  in  length,  and  the  angle  of 
the  faceboard  to  the  ground  is  about  28  degrees,  and  is  regu- 
lated by  the  attachment  to  the  tailboard.  The  Fresno  scraper 
is  most  satisfactory  in  handling  tough  earth  too  heavy  to  be 
handled  by  a  Buck  scraper,  and  which  would  even  give  trouble 
to  a  road  scraper.  This  implement  is  usually  drawn  by  four 
horses  and  handles  about  100  cubic  yards  a  day,  each  load 
averaging  a  third  of  a  cubic  yard. 

306.  Excavating  Machines. — One  of  the  most  popular 
ditching  machines  now  employed  in  the  West  is  the  New  Era 
ditcher  and  excavator,  which  consists  of  a  series  of  gang-ploughs 
suspended  on  wheels.  An  endless  belt  or  elevator  is  attached 
to  the  truck  above  these  ploughs  in  such  manner  that  it  catches 
the  dirt  turned  up  by  them  and  deposits  it  on  the  banks  of  the 
canal  (Fig.  100).  This  machine  requires  from  eight  to  twelve 
horses  and  three  men  to  operate  it,  its  maximum  lift  being 
about  10  feet,  while  each  plough  makes  a  furrow  12  inches  wide 
and  6  inches  deep.  These  machines  have  attained  an  average 
capacity  of  100  cubic  yards  per  linear  mile  and  handle  about 
1000  cubic  yards  in  a  day's  run.  They  are  of  use  not  only  in 
excavating  and  building  canals,  but  also  in  building  low  earth 
embankments  for  storage  reservoirs. 

The  most  elaborate  apparatus  yet  employed  in  canal  con- 
struction is  the  great  canal  excavator  built  by  the  San  Fran- 
cisco Bridge  Company.  This  machine  consists  of  abridge  truss 
supported  on  wheels  running  on  rails  on  either  bank  of  the  canal. 
This  deck  truss  has  on  it  a  track  on  which  the  engine-house 


EXCAVATING  MACHINES, 


327 


arid  machinery  travel  back  and  forth  across  the  canal,  and  the 
excavator  consists  of  a  dredging  arm  carrying  an  endless  chain 
of  buckets.  The  material  brought  up  by  these  is  deposited  on 
one  of  two  endless  belt-carriers  running  on  booms  which  dump 
it  on  either  spillbank.  The  engineer  can  cause  the  excavator 
to  move  across  the  canal  on  the  truss  bridge,  or  can  raise  or 
lower  the  excavating  arm  carrying  the  buckets,  causing  these 
to  move  forward  and  perform  their  work.  There  are  twenty- 


FiG.  100. — NEW  ERA  EXCAVATOR. 

six  of  these  buckets,  each  having  a  capacity  of  •£  cubic  yard, 
and  the  apparatus  will  excavate  3000  cubic  yards  a  day  in  hard- 
pan.  This  machine  has  been  found  cheapest  and  most  effec- 
tive in  material  so  hard  that  a  pick  will  hardly  penetrate  it,  and 
especially  in  excavating  under  water  where  scrapers  cannot  be 
used.  In  earth  it  has  excavated  from  4000  to  5000  cubic  yards 
a  day,  at  an  average  cost  of  7  cents  per  cubic  yard. 

Dredges  of  various  forms  are  employed  on  the  larger  canals 
to  remove  silt  which  may  be  deposited  in  them,  and  to  repair 
and  straighten  banks  which  have  been  cut  down  or  eroded  by 
the  action  of  the  water.  Such  dredges  are  usually  employed 
on  scows  or  flatboats,  and  are  operated  by  small  steam  engines, 


328  PUMPING,    TOOLS,    AND   MAINTENANCE. 

being  similar  in  design  and  in  construction  to  the  ordinary 
dredges  employed  in  river  and  harbor  work,  and  in  like  opera- 
tions. 

307.  Maintenance  and  Supervision  of  Canal  Works.— 
Careful  attention  should  be  paid  to  the  proper  maintenance 
and  the  making  of  all  needful  repairs  on  the  lines  of  canals, 
reservoirs,  and  other  irrigation  works.     The  expenditure  of  an 
exceeding  small  amount  of  time  or  money  in  repairing  an  in- 
jury  to  canal  banks  or  other  works  may,  if  done  in  time,  prevent 
great  destruction  of  life  and  property  consequent  on  an  injury 
to  the  canal  system.     In  order  that  these  repairs  may  be  intel- 
ligently made,  and  that  damage  to  the  canal  property  may  be 
discovered  in  time,  a  suitable  system  of  supervision  must  be 
inaugurated   upon    the   completion   of   construction.      Such  a 
system    should    include    an    engineer,   a    superintendent,    and 
patrolmen. 

308.  Sources  of  Impairment  of  Irrigation  Works. — These 
are  : 

1.  Erosion  of  the  canal  banks  by  water. 

2.  Filling  of  the  canal  channel  or  reservoir  from  deposition 
of  sediment. 

3.  Erosion   of  the  outer   banks   due  to    storm    and   flood 
waters. 

4.  Damage  from  cattle,  horses,  and  trespassers  destroying 
the  banks,  channel,  and  dams  by  walking  over  them. 

5.  Injury  or  destruction  to  the  headworks,  regulators,  es- 
capes, or  wasteways  by  floods. 

6.  Incendiarism. 

7.  Decay  in  timbers  forming  structures. 

8.  Destruction  of  earth  banks  due  to  burrowing  by  gophers. 

9.  Injury  from  growth  of  weeds  or  water  plants  choking  the 
channel,  and  thus  diminishing  its  discharge. 

The  first  and  second  causes  of  impairment  may  be  dimin- 
ished by  the  use  of  intelligent  engineering  skill  in  the  alignment 
and  construction  of  the  canals,  and  by  the  vigilance  of  patrols 
in  discovering  indications  of  erosion  and  rectifying  them.  If 
the  amount  of  sediment  deposited  is  large,  it  will  have  to  be 


INSPECTION.  329 

•removed  by  dredges  or  scrapers,  and  such  changes  will  have  to 
be  made  in  the  headworks  or  slope  of  the  canal  or  by  the  in- 
sertion of  flushing  escapes  as  to  rectify  them.  Little  injury 
should  be  caused  the  outer  banks  of  the  canal  by  storm  waters 
if  the  canal  is  properly  aligned  and  ample  provisions  made  for 
the  passage  of  drainage  channels.  Injury  due  to  rain  falling  on 
the  banks  may  be  reduced  to  a  minimum  by  the  encourage- 
ment of  the  growth  of  grass  and  trees. 

Damage  to  the  canal  from  the  fifth  and  seventh  causes 
may  be  provided  against  in  the  construction  by  building  the 
structure  of  some  permanent  material  as  masonry  or  iron,  and 
during  operation  by  proper  supervision  and  repairs*  of  the 
weakened  part.  Much  damage  may  result  from  the  burrowing 
of  gophers  and  moles.  This  can  only  be  prevented  by  careful 
supervision,  the  discovery  of  the  holes,  and  the  destruction  of 
the  pests.  The  discharge  of  a  canal  may  be  considerably  re- 
duced by  the  growth  of  aquatic  plants  and  willow  along  the 
banks.  This  is  to  be  prevented  only  by  pulling  up  or  mowing 
the  brush  or  by  destroying  it  by  fire  when  the  canal  is 
•empty. 

309.  Inspection. — In  order  that  the  supervision  and  inspec- 
tion of  works  may  be  properly  performed,  the  canal  line  should 
be  divided  into  a  number  of  sections,  each  of  which  should  be 
patrolled  by  a  ditch  rider,  while  the  whole  should  be  in  charge 
of  a  superintendent.  Where  the  line  is  long,  telephone  com- 
munication should  be  had  from  each  section  to  the  main  office 
of  the  engineer  and  superintendent.  In  addition  to  this  piles 
of  lumber  or  other  building  material  should  be  placed  at  each 
bridge,  escape,  or  other  work  on  a  canal,  and  by  this  means  any 
damage  inflicted  to  the  property  by  whatever  cause  may  be 
immediately  repaired  by  the  patrol,  or  he  may  telephone  to 
headquarters  for  further  assistance  and  proper  advice.  The 
length  of  a  division  of  the  patrol  should  be  regulated  by  the 
number  of  irrigation  outlets  and  the  character  of  the  works, 
and  they  should  be  of  such  length  that  every  portion  can  be 
visited  daily. 


330  PUMPING,    TOOLS,    AND   MAINTENANCE. 

310.  Works   of  Reference.    Pumping  Machinery  and 
Water  Pipes. 

BUTLER,   W.   P.     Irrigation    Manual.     Huronite    Printing    Company, 

Huron,  S.  D.,  1892. 
COLLYER,    F.     Pumps  and    Pumping   Machinery.     E.  &    F.  N.  Spon, 

London. 
CULLEN,  WILLIAM.    A  Practical  Treatise  on  the  Construction  of  Water 

Wheels.     E.  &  F.  N.  Spon,  London. 
FANNING,  J.  T.     Water  Supply  Engineering.     D.  Van  Nostrand  &  Co., 

New  York,  1890. 

HUGHES,  SAMUEL.     Water  Supply  of  Cities  and  Towns.    Crosby,  Lock- 
wood  &  Co.,  London,  1882. 

MAHAN,  F.  A.     Water  Wheels.     E.  &  F.  N.  Spon,  New  York. 
RONNA,  A.     Les  Irrigations.     Firmin-Didot  et  Cie,  Paris. 
TROWBRIDGE,  W.  P.    Turbine   Water  Wheels.      D.    Van  Nostrand  & 

Co.,  New  York. 
WOLFF,  A.  R.    The  Windmill  as  a  Prime  Mover.    John  Wiley  &  Sons, 

New  York. 
WEISBACH,  P.  J.,  and   DuBois,  A.  JAY.      Hydraulics  and   Hydraulic 

Motors.    John  Wiley  &  Sons,  New  York,  1889. 


INDEX. 


PACK 

Absorption 19 

Amount  of,  ine  Rservoirs  and  Canals 20 

Acre-foot 38 

Duty  of  Water  per 42 

Agra  Canal,  Iron  Aqueduct 135 

Scouring  Sluices 188 

Alessandro  Hydrant 214 

Alignment  of  Canals,  Obstacles  to 74 

and  Survey  of  Canals 73 

Alkali 32 

Causes  of 32 

Prevention  of 33 

Reference  Works  on 43 

Soil,  Chemical  Treatment  and  Leaching  of 34 

Allen,  C.  P , 201 

Appleton  Weir 128 

Application  of  Water,  Methods  of 204 

Aprons  to  Weirs 117 

Aqueducts  and  Flumes 172 

Iron 177 

"     Agra  Canal 188 

"     Bear  River  Canal,  Utah 178 

"     Henares  Canal,  Spain 179 

Masonry 181 

Nadrai,  over  Kali  Nadi  on  Lower  Ganges  Canal,  India 181 

Solani  River,  Ganges  Canal,  India 77,  81 

Areal  Duty  of  Water 42 

Arizona  Canal,  Fall  on 162 

Plan  of  Headworks 143 

Regulator  Gates 148 

Arizona  Weir ill 

331 


332  INDEX. 

PAGE 

Arrangement  of  Canal  Head 145 

Artesian  Wells 29 

Sources  of 28 

Ashlar  Masonry 267 

Ashti  Dam 231,  305 

Atmospheric  Pressure 46 

Automatic  Shutters  and  Gates 386 

Sluice  Gates 136 

"     Soane  Weir 138 

"      Shutters,  Mahanuddy  Weir 137 

Available  Annual  Flow  of  Streams 27 

Baker,  Ira  O 255 

Banks  of  Canals,  Side  Slopes  and  Top  Widths  of 91 

Bari  Doab  Canal,  Drainage  Diversion 169 

Rapids 169 

Bear  River  Weir 112 

Canal,  Cross-section  in  Rock , . . . 94 

"       Fall  163 

"        Iron  Aqueduct ....   178 

"       Regulator  Gates 151 

Bear  Valley  Dam 264,  266,  298,  314 

Beetaloo  Dam 268,  287 

Beresford,  J.  S 19,  20,  194 

Betwa  Canal,  Drainage  Diversion 169 

Dam 268,  291,  304 

Bhatgur  Dam 281,  304,  307 

Bifurcation,  Del  Norte  Canal,  Col 199 

Big  Drop,  Grand  River  Canal,  Col 167 

Borings  on  Canal  Locations 76 

Bowlder  and  Brush  Weirs 98 

Bowman  Dam 245 

Brush  and  Bowlder  Weirs 98 

Buchanan  Dam 266 

Buck  Scraper 325 

Calloway  Canal,  Cross-section 92 

"      Distributary  Heads 198 

'"      Escapes 156 

"      Regulator. 146 

Weir 103 

Canal  Alignment,  Ganges  Canal  as  an  Example , 76 

Obstacles  to 74 

Turlock  Canal  as  an  Example 79 

Canal  Cross-sections,  Form  of.    89 

Rock 93 

Canal  Grades  for  given  Velocities 87 


INDEX.  333 

PACK. 

Canal  Head,  Arrangement  of 145 

Locations,  Borings  on 76 

Trial  Pits  on 76 

Survey,  Permanent  Marks  on = 76 

System,  Parts  of 69 

Water,  Measurement  of 61 

"      Methods  of  Measurement  of 62 

Works,  Maintenance  and  Supervision  of 328 

Work,  Sidehill > 74 

Canals  and  Canal  Works,  Works  of  Reference 215 

Curvature  on 75 

Deltaic  69. 

Dimensions  and  Cost  of  some  Perennial.  * 70- 

Efficiency  of 194 

Inspection  of 329 

Inundation „ 68 

Limiting  Velocity  on 86. 

Navigation  and  Irrigation 67 

Perennial 68 

Prevention  of  Sedimentation  in 35 

and  Reservoirs,  Amount  of  Absorption  in 20 

Slope  and  Cross-section  of 85,  88 

Survey  and  Alignment  of 73 

Carpenter,  L.  G 59 

Castlewood  Dam 247 

Causes  of  Alkali 32 

Cavour  Canal,  Inverted  Siphon  under  River  Sesia 190 

Centers  of  Pressure  of  Water 46 

Central  Irrigation  District,  Inverted  Siphon 186 

Centrifugal  Pumps 322 

Check-Levees,  Flooding  by 206 

Chemical  and  Physical  Properties  of  Water 44 

Treatment  of  Alkali  Soil 34 

Chezy's  Formula  of  Flow 50- 

Chutes  of  Wood 167 

Cippoletti's  Formula  of  Flow  over  Weirs 59 

Closed  and  Open  Weirs 99 

Coefficient  C  for  Kutter's  Formula,  Table  of 50 

of  Friction  in  Masonry 252 

Colorado  Current  Meter 53 

River  Dam,  Texas 297 

Wooden  Pipe 202: 

Composite  Gravel  and  Rock  Weir 115 

Concrete 269 

Construction  of  Crib  Weirs 115. 


334  INDEX. 

PACK 

Construction  of  Embankment.  ..,.•.... 331 

in  Flowing  Streams 274 

of  Flumes 175 

of  Masonry  Dam,  Details  of 271 

Contracts  and  Specifications 275 

Core  Walls,  Masonry 227,  229 

Oost  and  Dimension  of  Storage  Reservoirs 221 

Perennial  Canals 68 

-Cost  of  Irrigation 3 

Crib  Dams 244 

Foundations  for  Masonry  Weirs 123 

and  Pile  Foundations  for  Masonry  Weirs 122 

and  Rock  Weirs , in 

Weirs,  Construction  of 115 

Cribwork,  Underground 316 

Cross-section  of  Bear  River  Canal  in  Rock 94 

Galloway  Canal 92 

Canals 85,  88 

Canals,  Form  of 89 

Canals  in  Rock 93 

Canal  with  Sub-grade  92 

Turlock  Canal  in  Rock ....     93 

Croton  Dam,  New,  at  Cornell's,  N.  Y 268,  282,  304 

Croton  Weir  or  Dam 1 23 

Crushing,  Stability  against,  in  Masonry  Dams 254 

Current  Meters 53 

Colorado 53 

Haskell 54 

Rating  the 55 

Use  of 55 

Curved  Dam,  Design  of 265 

Masonry  Dam 261 

Curvature  on  Canals 75 

.Dam,  Ashti 232,  305 

Bear  Valley 264,  266,  298,  314 

Beetaloo 268,  287 

Betwa 268,  291,  304 

Bhatgur 281,  304,  307 

Bowman 245 

Buchanan 266 

Castlewood 247 

Colorado  River 297 

Croton,  N.  Y 125 

Design  of  Curved 265 

Earth  with  Masonry  Retaining  Wall 238 


INDEX.  335 

PACK 

Dam,   Ekruk 239 

English 246 

Folsom 295,  304,  310 

Furens 277 

Geelong 268 

Gran  Cheurfas 278 

Gros  Bois 256 

Idaho 242,  305 

Kabra 239 

Loose-Rock  with  Masonry  Retaining  Walls 246 

New  Croton,  Cornell's,  N.  Y 268,  282,  304 

Pecos 241,  305 

Periar 268,  269,  285,  305 

Profile  of 260 

Profile  Type  for  Masonry 259,  261,  263 

Quaker  Bridge 256 

San  Fernando 274 

San  Mateo 268,  269,  287,  315 

Sweetwater 264,  289,  314 

Tansa 279,  304 

Turlock f.,  .295,  304 

Verdon 256 

Vir 268 

Vyrn  wy 289,  304,  3 1 5 

Walnut  Grove  244 

Zola 264,  266,  298 

Dams,    Crib 245 

Curved  Masonry 261 

Details  of  Construction  of  Masonry 271 

Dimensions  of  Earth 225 

Diversion 131 

Earth k    224 

Earth  and  Loose-Rock 240 

Examples  of  Masonry 276 

Foundations  of • 267 

Foundations  of  Earth . .   226 

Inlet ;  for  Drainage , 170 

Limiting  Pressures  in  Masonry 255 

Loose-Rock 243 

Material  of  Masonry 267 

Puddle  Walls  and  Faces  of  Earth 230 

Rock-filled 244 

Springs  in  Foundations  of 229 

Stability  against  Crushing 254 

Stability  of  Gravity 249 


336  INDEX. 


Dams,    Stability  of,  against  Overturning 256 

Stability  against  Sliding 251 

Submerged ...    273 

Theory  of  Masonry . .   248 

D'Arcy's  Formula  of  Flow 49 

Del  Norte  Canal  Distributing  Heads 199 

Regular  Gates 149 

Screw  Regulator  Gate 151 

Deltaic  Canals 69 

Diagram  of  Discharges  of  Western  Rivers 26 

Dickens,  Col.  C.  H.t  Formula  for  Runoff 23 

Discharge  Diagram  for  Western  Rivers 26 

over  Rectangular  Weirs,  Table  of 60 

of  Streams 51 

"         "         Mean 27 

"         "         in  Seasons  of  Minimum  Rainfall 25 

of  Waste  Weirs 303 

of  Western  Rivers 26 

Ditches,  Private 196 

Diversion  Line 72 

Weirs 97 

Divisors,  Water 65 

Distributary  Channels  in  Earth 198 

Heads,  Calloway  Canal,  Cal 198 

Del  Norte  Canal,  Col 199, 

"       of  Masonry 201 

of  Wood 1-98 

Pipes  of  Iron,  Steel,  or  Wood 201 

Distributaries,  Design  of 193 

Dimensions  of  197 

Location  of 191 

Object  and  Types  of 191 

Distribution  of  Rainfall  in  Detail 6 

Water,  Rotation  in ....    203 

Drainage. 34 

Crossing  at  Level 1 70 

Cuts • 169 

Diversion,  Bari  Doab  Canal,  India 169 

"          Betwa  Canal,  India 170 

Inlet  Dams  for. ...    1 70 

Works 169, 

Dredges 327 

Duty  of  Water . .    38 

per  Acre-foot 42 

Linear  and  Areal 4.2 


INDEX.  *  337 

PAGE 

Duty  of  Water,  Measurement  of 40 

Reference  Works  on , 43 

per  Second-foot 40 

Table  of 41 

Dyas,  Col.  J.  H 160 

Earth  Dams,  Construction  of 231 

Dimensions  of 224, 

or  Embankments 225 

Foundations  of 225 

with  Masonry  Retaining  Wall 237 

Puddle  Walls  and  Faces 230 

Earth,  Distributary  Channels  in rgS 

Evaporation  from i& 

Earth  Embankment,  Homogeneous 227,  233, 

Slope  and  Paving  of 235 

Earth  and  Loose-Rock  Dams 240 

Earthwork,  Shrinkage  of 93, 

English  Dam   246. 

Effect  of  Evaporation  on  Water  Storage 18 

Efficiency  of  a  Canal 194 

Egypt,  Area  irrigated  in I 

Ekruk  Dam 239- 

Elevators 319 

Embankment,  Construction  of 231 

Earth  Dams , 224 

Homogeneous 227,  233 

Material 234 

with  Masonry  Retaining  Wall 237 

Slope  and  Paving  of 235 

Engines,  Pumping 323 

Escapes 154 

Bear  River  Canal,  Utah 156 

Galloway  Canal,  Cal 156 

Heads,  Design  of 156 

Highline  Canal,  Col 156 

Idaho  Canal    156 

Location  and  Characteristics  of 155 

Turlock  Canal,  Cal 1 57 

Evaporating  Pan 14 

Evaporation,  Amount  of 15 

Effect  of,  on  Water  Storage 18 

from  Earth 18 

Measurement  of 13 

Percolation  and  Runoff,  Works  of  Reference 27 

Phenomena 13 


338  INDEX. 

PAGE 

Evaporation,  from  Snow  and  Ice 17 

Table  of  Depth  of 16,  17 

Evaporometer,  Piche 15 

Excavating  Machines 326 

Excavator,  New  Era 326 

Faces,  Puddle  of  Earth  Dams 230 

Factors  Affecting  Flow  of  Water 48 

Fall  of    Wood,  Simple  Vertical ....   162 

Wooden,  with  Water-cushion 165 

on  Arizona  Canal 163 

Bear  River  Canal,  Utah 165 

Fresno  Canal 165 

Turlock  Canal,  California 165 

Falls  of  Masonry 167 

and  Rapids 160 

Retarding  Velocity  of  Approach  to,  by  contracting  Channel  above. .    161 

by  Flashboards 160 

by  Gratings 161 

Falling  Water,  Scouring  Effect  of 1 16 

Fanning,  J.  T 23,  25 

Fertilizing  Effects  of  Sediment. 36 

Flashboard  or  Open-Frame  Weirs roi 

Regulators  of  Wood 146 

Flood  Discharges  of  Streams 25 

Flooding  by  Check-Levees 206 

and  Furrow  Irrigation  Combined  210 

of  Sidehill  Meadows 205 

by  Squares 207 

by  Terraces 208 

Flynn,  P.  J 161 

Flow,  Annual,  of  Available  Streams 27 

in  Open  Channels,  Formulas  of 49 

of  Water,  Units  of  Measure  of 38 

Flume,  Highline  Canal,  Col 173 

on  Pecos  Canal,  N.  M 177 

San  Diego,  Cal 173,  175 

Trestles 177 

Flumes  and  Aqueducts 172 

Construction  of 175 

Rating 64 

Sidehill 173 

Folsom  Canal,  Hydraulic  Lifting  Gate 153 

"      Sand  Gates 157 

Dam 295,  304,  310 

Foote,  A.  D. 62 


INDEX.                          *  339 

PACK 

Foote's  Water  Meter 63 

Foundations  of  Dams,  Springs  in 228 

Earth  Dams 226 

Masonry  Core  and  Puddle  Wall 227 

"       Dams 267 

France,  Area  irrigated  in i 

Francis,  J.  B 58,  254 

Francis  Formulas  of  Flow  over  Weirs 58 

Fresno  Canal,  Fall  on 165 

Friction,  Coefficient  of,  in  Masonry 262 

Furens  Dam 277 

Furrow  and  Flooding  combined 210 

Irrigation 209 

Furrows,  Irrigation  by  Small 211 

•Ganges  Canal,  as  an  Example  of  Canal  Alignment 76 

Headworks  and  Plan  of 141 

Ranipur  Superpassage 77,  183 

Regulator  Gates 147 

Rutmoo  Level  Crossing 77,  172 

Solani  Aqueduct 77,  181 

'Gate  Towers 312 

Examples  of 314 

Gates,  Automatic  Weir  306 

•Gauge  Heights,  Weir 61 

•Gauging  Rainfall 1 1 

Stations 54 

Station,  Rating  the 56 

Stream  Velocities 52 

Gearing,  Regulator  Gates  raised  by 148 

Geelong  Dam 268 

Geology  of  Reservoir  Site   220 

Gila  River  Valley,  Precipitation  in 6 

Grade  for  given  Velocities  on  Canals 87 

Gran  Cheurfas  Dam 278 

Grand  River  Canal,  Big  Drop 167 

Gratings  to  Retard  Velocity  of  Approach  to  Falls 161 

Gravity  Dams,  Stability  of 249 

Gravity  and  Lift  Irrigation 66 

Gravel  and  Rock  Weirs,  Composite 115 

Greaves,  Charles iS 

Gros  Bois  Dam 256 

Hartt,  A 323 

Haskell,  Current  Meter 54 

Headworks  of  Arizona  Canal,  Plan  of 142 

Arrangement  of 145 


340  INDEX. 

PAGE 

Head  works,  Character  of 96 

Ganges  Canal,  India 141 

Idaho  Canal,  Plan  of 143. 

Location  of 72,  95 

Height  of  Waves 236- 

Henares  Canal  Iron  Aqueduct,  Spain 179, 

Weir,  Spain 127 

Highline  Canal,  Bench  Flume 173, 

Escapes  156. 

Scouring  Sluices 134 

Holyoke  Weir 113 

Homogeneous  Embankment 227,  233 

Huffer  Pumps. 323 

Humphreys  and  Abbott 49 

Hydrant,  Alessandro 214 

Hydraulic  Lifting  Regulator  Gate,  Folsom  Canal,  Cal 153 

Hydraulics,  Works  of  Reference  on 65 

Ice,  Evaporation  from 17 

Idaho  Canal  Dam 240,  30 j 

Escapes 156- 

Plan  of  Headworks 143 

Rapids  on  Phyllis  Branch 169. 

Rolling  Regulator  Gates 151 

Sliding  Regulator  Gates , 149,  151 

Impairment  of  Irrigation  Works,  Sources  of 328 

India,  Precipitation  in ....    5 

Inlet  Dams  for  Drainage 170- 

Inspection  of  Canals 329 

Interior  Slope  and  Paving  of  Embankment 235 

Inundation  Canals 68 

Inverted  Siphons.... 185,  189 

of  Masonry 189 

Investment,  Value  of  Irrigation  as  an 2 

Iron  Aqueducts 177 

Iron,  Steel,  and  Wooden  Distributary  Pipes 201 

Irrigation,  Cost  and  Returns  of , 3 

Extent  of I,  3 

by  Flooding  and  Furrows  combined 210 

by  Furrows 209 

Harmful  Effects  of 32 

Lift  and  Gravity 66 

and  Navigation  Canals , 67 

Period 39 

Pumping  or  Lift 318 

Relation  of  Rainfall  to £ 


INDEX.  341 

PAGE 

Irrigation,  by  Small  Furows 21  i 

Subsurface 212 

Table  of  Extent  and  Cost  of 3 

Tools 324 

Works,  Classes  of 66 

"        Control  of I 

"        Sources  of  Impairment  of , .  328 

Italy,  Area  irrigated  in I 

Precipitation  in 5 

Kabra  Dam 239 

Kao  Torrent  Siphon  Aqueduct  on  Soane  Canal,  India 189 

Krantz,  J.  B 249 

Kmter's  Formula  of  Flow 49 

Land,  Percentage  of  Waste 42 

and  Water  Supply,  Relation  between 72 

and  Water  Supply,  Relation,  to  Reservoir  Site 216 

Lawrence  Weir 131 

Laying  Sub-irrigating  Pipes,  Method  of 213 

Leaching  of  Alkali  Soil 34 

Level  Crossings  of  Drainage 170 

Rutmoo 77,  172 

Turlock  Canal,  Cal. 171 

Lever,  Wooden  Regulator  Gate  raised  by 146 

Lift  and  Gravity  Irrigation 66 

Irrigation  or  Pumping 318 

Limiting  Pressures  in  Masonry  Dams 255 

Linear  Duty  of  Water 42 

Little  Kukuna  Weir 1 16 

Location  and  Characteristics  of  Escapes 155 

of  Distributaries 191 

of  Headworks 72,  95 

Survey,  and  Alignment  of  Canals 73 

Loose-Rock  and  Earth  Dams 240 

Dams 242 

"      with  Masonry  Retaining  Walls 246 

Lower  Ganges  Canal,  Nadrai  Aqueduct,  India •  •  •  •  * J8i 

Machines,  Excavating 326 

Mahanuddy  Sluice  Shutters 137 

Maintenance  of  Canal  Works 328 

Material  of  Embankment 234 

Masonry  Aqueducts 181 

Ashlar 267 

Coefficient  of  Friction  in 252 

Cores.   227,  229 

"      Foundation  of 226 


342  INDEX. 

PAGE: 

Masonry  Dams,  Curved 261 

"       Details  of  Construction 271 

"       Examples  of 276 

' '       Foundations  of 267 

"       Limiting  Pressures  in 255 

"       Material  of 267 

"       Profile  Type  for 259,261,263 

"       Theory  of 248 

Distributary  Head 201 

Falls 167 

Rapids 169 

Retaining  Wall,  Embankment  with 237 

Weirs 121 

"      Founded  on  Piles 122 

"      Founded  on  Piles  and  Cribs 123 

"      Founded  on  Wells 126. 

"      Open  Indian  Type 104 

Material  of  Masonry  Dams 267 

Mean  Discharge  of  Streams 27 

Mean  and  Surface  Velocities 52 

Meadows,  Sidehill  Flooding  of 205 

Measure,  Units  of,  for  Water  Duty  and  Flow 38- 

Measurement  of  Canal  Water 61 

Evaporation 131 

Water  Du  ty 40- 

Measures  of  Water,  Table  of  Units  of ;     39 

Measuring  Stream  Velocities 52 

Sub-irrigation  Waters 214 

Weirs 57 

Meiers,  Current , 53 

Miner's  Inch . .  38 

Molesworth,  Guilford  L 259 

Profile  Type  for  Masonry  Dam 259 

Monte  Vista  Canal  Scouring  Sluices 1 35 

Weir 101 

Mot 318 

Motion  of  Water 46 

Nadrai  Aqueduct,  Lower  Ganges  Canal,  India 181 

Navigation  and  Irrigation  Canals 67 

Newark  Weir 1 29- 

New  Croton  Dam,  Cornell's,  N.  Y 268,  282,  304 

New  Era  Excavator ..." 326> 

Norwich  Water  Power  Co.'s  Weir 122 

Nye  Pumps 323 

Object  and  Ty  pes  of  Distributaries iQt 


INDEX.  345- 

PAGE 

Obstacles  to  Alignment  of  Canals ...     74 

Ogee-shaped  Weirs 118 

Open  Channels,  Formulas  of  Flow  in 49 

and  Closed  Weirs 99 

Frame  or  Flashboard  Weirs 101 

Iron  Frame  WTeirs,   French 109 

Masonry  Weirs,  India  Type 104 

Outlet  Sluices 310 

Examples  of 314 

Overturning,  Stability  of  Dams  against 256 

Paecottah , .   318 

Parts  of  a  Canal  System 69 

Paving  of  Embankment 236 

Pecos  Canal  Flume 177 

Dam 239,  305 

Valley,  Precipitation  in 6 

Pelletreau,  M 264 

Pequannotk  Weir 129 

Percentage  of  Waste  Land ....     42 

Percolation,  Amount  of 18 

Prevention  of 20 

Runoff  and  Evaporation,  Works  of  Reference 27 

Perennial  Canals 68,  70 

Periar  Dam 268,  269,  285,  305 

Permanent  Marks  on  Canal  Surveys 76 

Persian  Wheel 318 

Phoenix,  Precipitation  at 8 

Physical  and  Chemical  Properties  of  Water 44 

Piche  Evaporometer 15 

Pile  Foundations  for  Masonry  Weirs 122 

Weirs. 99 

Pipes,  Iron  and  Steel  and  Wooden  Distributary 201 

Method  of  Laying  Sub-irrigation 213 

Sub-irrigation ' 213, 

Precipitation  by  River  Basins,  Table  of 9, 

States,  Table  of 10 

Pressure,  Atmospheric 46 

Limiting,  in  Masonry  Dams 255 

of  Water 45 

Private  Watercourses 196 

Profile  of  Dam 260 

Type  for  Masonry  Dam 259,  261,  263 

Puddle  Trench 231 

Walls 227,  230 

and  Faces 230 


344  INDEX. 


Puddle  Walls,  Foundations  of 226 

Pumping  Engines 323 

or  Lift  Irrigation 317 

Pumps,  Centrifugal 322 

Huffer  and  Nye 323 

Steam , , 321 

Quaker  Bridge  Dam 256 

Rainfall, 6 

Discharge  of  Streams  in  Seasons  of  Minimum 25 

Distribution  in  Detail ,       6 

Gauging n 

Relation  of,  to  Irrigation 5 

on  River  Basins 9 

Statistics,  General 6 

Statistics  by  States 9 

Works  of  Reference  on 12 

Great  - 7 

Ranipur  Superpassage 77,  183 

Rapids,  Bari  Doab  Canal,  India 169 

and  Falls 160 

Masonry « 169 

Phyllis  Branch,  Idaho  Canal 169 

Wooden ,  . . .   167 

Rating 64 

Current  Meter 55 

Flumes 64 

Gauging  Station 56 

Rectangular  Measuring  Weir 57 

Pile  Weirs 99 

Reference  Works  :  Alkali,  Sedimentation,  and  Duty  of  Water 43 

Artesian  Wells 31 

Canals  and  Canal  Works 215 

Evaporation,  Percolation,  and  Runoff 27 

Hydraulics 65 

on  Rainfall 121 

Storage  Works 300 

Regimen  of  Western  Rivers 25 

Regulator  Gates,  Arizona  Canal 148 

Bear  River  Canal,  Utah 151 

Del  Norte  Canal,  Col 149 

Del  Norte  Screw 151 

Folsom  Canal,  Hydraulic  Lifting 153 

Ganges  Canal,  India 147 

Lifted  by  Travelling  Winch 148 

Raised  by  Gearing  or  Screw 148 


INDEX,  345 

PAGE 

Kegulator  Gates   Rolling,  Idaho  Canal 151 

Sliding,  Idaho  Canal 149 

Soane  Canal,  India 147 

of  Wood  lifted  by  Lever 146 

of  Wood  lifted  by  Windlass 147 

Regulators,  Callovvay  Canal,  Cal 146 

Classification  of 143 

Form  of 144 

Relation  of  Weirs  to 139 

Wooden  Flashboard 146 

Reinold,  E.  K 307 

Reservoir  Site,  Character  of 218 

Geology  of 220 

Relation  of,  to  Land  and  Water  Supply 2iO 

Topography  and  Survey  of 218 

Reservoir,  Vir,  India 309 

Reservoirs  and  Canals,  Amount  of  Absorption  in 20 

Cost  and  Dimensions  of  some  Storage 221 

Prevention  of  Sedimentation  in 35 

Retaining  Wall  of  Masonry,  Embankment  with * . . .   237 

to  Loose-Rock  Dam 246 

Retarding  Velocity  of  Approach  by  Contracting  Channel  above  Fall 161 

Flashboards  on  Fall  Crest 160 

Gratings  on  Fall  Crest 161 

Returns  of  Irrigation 3 

Rio  Grande  River,  Precipitation  in 6 

River  Basins,  Rainfall  on g 

Rivers,  Western,  Discharge  of 26 

Regimen  of 25 

Rock  and  Crib  Weirs 1 1 1 

Cross-section  of  Canals 93 

Foundations  for  Masonry  Weirs ...    126 

and  Gravel  Weirs,  Composite „ ,   115 

Rock-filled  Dams 242 

Rollerway  and  Ogee-shaped  Weirs 118 

Rolling  Regulator  Gates,  Idaho  Canal 151 

Rotation  in  Water  Distribution 202 

Runoff 22 

Examples  of 24 

Formulas  of 22 

Percolation  and  Evaporation,  Works  of  Reference 27 

Variability  of 22 

Russell,  T 15 

Rutmoo,  Level  Crossing 77,  172 

Ry  ves,  Col.,  Formula  for  Runoff 23 


INDEX. 


Sacramento  Valley,  Precipitation  in 7 

San  Diego  Flume 173,  175. 

Weir. 127 

San  Fernando  Dam 274 

San  Joaquin  Valley,  Precipitation  in 7 

San  Mateo  Dam 268,  269,  289,  315 

Sand  Gates 157 

Second-foot 38 

Duty  of  Water  per 40 

Sediment,  Amount  of 35 

Fertilizing  Effects  of 36 

Sedimentation,  Prevention  of,  in  Reservoirs  and  Canals 35. 

Reference  Works  on 43 

Seepage  Water ,  . 21 

Service  Period 39, 

Sesia  Siphon  on  Cavour  Canal,  Italy 190 

Scouring  Effect  of  Falling  Water 116 

Scouring  Sluices , 133 

Agra  Canal,  India 135 

Examples  of 135 

Highline  Canal,  Col 1 34 

Monte  Vista  Canal,  Col 135 

Scrapers 325 

Scraper,  Buck 325 

Screw  Regulator  Gate,  Del  Norte  Canal,  Col 151 

Screw,  Regulator  Gate  raised  by 145 

Shutters,  Automatic  Weir 306 

Shrinkage  of  Earthwork 93 

Side  Slopes  of  Canal  Banks 91 

Sidehill  Canal  Work 74 

"    Turlock  Canal 81 

Flumes 173: 

Sidhnai  Weir , 107 

Silt 35 

Sirhind  Canal,  Siphon  under  Hurron  Torrent ....  190 

Siphon-Aqueduct  on  Soane  Canal  under  Kao  Torrent 189 

Siphon,  Stony  Creek;  on  Central  Irrigatiou  District  Canal,  Cal 186 

under  Hurron  Torrent  on  Sirhind  Canal,  India 1 90 

Inverted,  under  River  Sesia  on  Cavour  Canal,  Italy 190 

Siphons,  Inverted 185,  189 

Masonry  Inverted 189 

Sliding  Regulator  Gates,  Idaho  Canal 151 

Stability  against,  in  Masonry  Dams 251 

Slope  of  Canals 85 

Embankment 236- 


INDEX.  347 

J'AGtt 

Slope ,   Excessive 1 59 

Sluice  Gates,  Automatic 136,  138 

Shutters,  Mahanuddy  Automatic 137 

Sluices,  Outlet 310 

Scouring 133. 

Snow,  Evaporation  from 17 

Soane  Automatic  Sluice  Gates 138 

Canal,  Regulator  Gates 148 

"        Siphon-Aqueduct  under  Kao  Torrent 189 

Weir 106 

Soil,  Depth  of  Water  Required  to  Soak 41 

Solani  Aqueduct,  Ganges  Canal,  India 77,  181 

Sources  of  Earth  Waters 28 

Springs  and  Artesian  Wells 281 

Supply 67 

Specifications  and  Contracts ." 275 

Springs  in  Foundations  of  Dams. 225 

Sources  of 28 

Squares,  Flooding  by 207 

Stability  against  Crushing  in  Masonry  Dams 254 

against  Sliding  in  Masonry  Dams 251 

of  Dams  against  Overturning ,  256 

Gravity  Dams 249 

Steam  Pump *2i 

Steel,  Iron  and  Wooden  Distributary  Pipes 201 

Storage  Reservoirs,  Cost  and  Dimensions  of  some 221 

of  Water,  Effect  of  Evaporation  on , 18 

Works,  Classes  of 216 

4 '        Works  of  Reference  on 300 

Stream  Velocities,  Measuring  or  Gauging 52 

Streams,  Available  Annual  Flow  of 27 

Construction  in  Flowing 274 

Discharge  of;  and  Velocities  of  Flow  of 51 

Flood  Discharges  of ." 25 

Mean  Discharge  of 27 

Sub-canals 30 

Sub-grade  to  Canal  Cross-section . .  92 

Sub-irrigation  Pipes 212 

"      Method  of  Laying 213 

Waters,  Measurement  of - 214 

Submerged  Dams 273 

Sub-supply  Tunnels 30 

Sub-surface  Irrigation 212 

Water  Sources 28 

Suddenness  of  Great  Storms 8 


34$  INDEX. 


Superpassages 1 8  r 

Superpassage    on  Ganges  Canal  over  Ranipur  Torrent 77,  183 

of  Iron,  Agra  Canal,  India 183 

Supervision  of  Canal  Works 328 

Supply,  Sources  of 67 

Supplying  Capacity  of  Wells 30 

Surface  and  Mean  Velocities 52 

Survey  and  Alignment  of  Canals 73 

Topography  of  Reservoir  Site 218 

Sweetwater  Dam 264,  289,  314 

Table,  Coefficient  C  for  Kutter's  Formula 50 

Coefficients  of  Friction  in  Masonry 252 

Cost  and  Dimensions  of  some  Storage  Reservoirs 221 

Depth  of  Evaporation 16,  17 

Dimensions  and  Cost  of  some  Perennial  Canals 79 

Discharge  over  Rectangular  Weirs 60 

Duty  of  Water 41 

Extent  and  Cost  of  Irrigation 3 

Precipitation  by  River  Basins 9 

Precipitation  by  States 10 

Units  of  Measure  for  Water 39 

Wegman  n's  Practical  Profile  Type 262 

Tansa  Dam 279,  304 

Terraces,  Flooding  by 208 

Theory  of  Masonry  Dams 248 

Tools,  Irrigation 325 

Topography  and  Survey  of  Reservoir  Site 218 

Top  Width  of  Canal  Banks 91 

Towers,  Gate 312 

Trapezoidal  Weirs 59 

Trench,  Puddle,  in  Earth  Dams :   231 

Trestles,  Flume „ 177 

Trial  Pits  on  Canal  Locations 76 

Tunnels  for  Sub-supply 301 

Turlock  Canal 82,  84 

Underground 317 

Turlock  Canal,  Cross-section  in  Rock   93 

Escapes 157 

as  an  Example  of  Canal  Adjustment 79 

Fall 165 

Level  Crossings j 72 

Sidehill  Works 81 

Tunnels 82,  84 

Turlock  Dam 295,  304 

Undergreund  Cribwork  or  Tunnels 316 


INDEX.  349 

PAGE 

Undersluices 309 

Examples  of 309 

United  States,  Area  irrigated  in I 

Units  of  Measure  for  Water  Duty  and  Flow 38 

Valve  Chambers 312 

Variability  of  Runoff 22 

Velocity  of  Approach,  Retarding  by  Contracting  Channel  above  Fall 161 

Flashboards  on  Fall  Crest 160 

Gratings  on  Crest  of  Fall 161 

Velocity,  Limiting,  on  Canals 86 

Velocities  on  Canals  for  given  Grades 87 

of  Flow 51 

"      "       Formula  for 48 

'•  Streams,  Measuring  or  Gauging 52 

Surface  and  Mean 52 

Verdon  Dam 256 

Vertical  Fall  of  Wood 162 

Vir  Dam 268 

Reservoir 309 

Weir 129 

Vischer,  Hubert 265 

Vyrnwy  Dam 291,  304,  315 

Wagoner,  Luther 265 

Walls,  Puddle 229 

in  Earth  Dams 230 

Walnut  Grove  Dam 244 

Waste  Land,  Percentage  of 42 

Waste  Weirs,  Discharge  of 303 

Shapes  of 305 

Wastevvays   301 

Character  and  Design  of 302 

Classes  of . . . 304 

Examples  of 305 

Water,  Centers  of  Pressure  of, 46 

Chemical  and  Physical  Properties  of 44 

Courses,  Private = 196 

Depth  of,  required  to  Soak  Soil 41 

Distribution,  Rotation  in 203 

Divisors 65 

Duty  of 38 

' '     Linear  and  Areal 42 

"     Reference  Works  on ....   43. 

' '     Units  of  Measure  for 38 

Excessive  Use  of 35 

Water,  Factors  affecting  Flow  of ' 4& 


350  INDEX. 


Water,  Measurement  of  Sub-irrigation 214 

Meter,  Foote's 63 

Methods  of  Applying 204 

Motion  of 46 

Pressure  of 45 

Scouring  Effect  of  Falling. 116 

Seepage 21 

Sources  of 28 

Sources,  Other  Sub-surface 30 

Storage,  Effect  of  Evaporation  on 18 

Supply  and  Land,  Relation  between 72 

"         "         "             "         of  Reservoir  Site  to 217 

Weight  of 44 

Water-cushions , 119 

Water-cushion  on  Wooden  Fall 165 

Water-logging 33 

Prevention  of 33 

Water-wheels 320 

Wave  Heights  and  Fetch 237 

Weeds 37 

Wegmann,   Edward,  Jr 257 

Profile  Type  for  Masonry  Dam 263 

Weight  of  Water 44 

Wells,  Artesian 29 

"        Reference  Works 3 

as  Foundations  for  Masonry  Weirs 1 26 

Supplying  Capacity  of 30 

"Weir  at  Appleton,  Miss 127 

Aprons , 117 

Arizona  Canal in 

Bear  River  Canal 112 

Galloway  Canal 103 

'Composite,  of  Gravel  and  Rock 115 

'Conditions  of  using  Rectangular 58 

Croton. 125 

Formulas,  Francis 58 

Gates  and  Shutters,  Automatic 306 

Gauge  Heights 61 

Jienares,  Spain 127 

,at  Holyoke,  Mass 113 

.-Little  Kukuna 116 

Merrimac  at  Lawrence,  Mass 131 

Monte  Vista  Canal 101 

of  Norwich  Water  Power  Co.,  Conn 122 

.across  the  Pequaunock-  River  at  Newark 129 


INDEX.  351 

PACK 

Weir  San  Diego,  Cal 127 

Sidhnai  Canal 107 

Soane  Canal 106 

at  Vir,    India 129 

Weirs  of  Brush  and  Bowlders 98 

Classes  of 98 

Construction  of  Crib   115 

Crib  and  Rock in 

Diversion 97 

Flashboard  or  Open-Frame 101 

Masonry 121 

founded  on  Cribs 123 

"     Piles 122 

"       "     and  Cribs 123 

"     Wells 126 

Open  Indian  Type 104 

Measuring. 57 

Open  and  Closed 99 

Open  Iron  Frame,  French 109 

Pile 99 

Relation  of,  to  Regulators 139 

founded  on  Rock   126 

with  Rollerway  or  Ogee  Shapes 118 

Table  of  Discharge  over  Rectangular 60 

Trapezoidal 59 

Wheel,  Persian 318 

Windlass,  Wooden  Regulator.  Gate  raised  by 146 

Windmills 319 

Winch,  Regulator  Gate  lifted  by  Travelling 147 

Works  on  Canals,  Maintenance  and  Supervision  of 328 

Works  of  Reference,  Alkali,  Sedimentation  and  Duty  of  Water.    43 

Artesian  Wells 31 

Canal  and  Canal  Works 215 

Evaporation,  Percolation,  and  Runoff 27 

Hydraulics 65 

Precipitation 12 

Pumping 330 

Storage  Works . , 300 

Wooden  Distributary  Heads 198 

Fall  with  Water-cushion 165 

Flashboard  Regulators. 146 

Rapids  or  Chutes 167 

Regulator  Gate  lifted  by  Lever 146 

"       "    Windlass 146 

Zola  Dam 264,  266,  298 


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